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<?xml version="1.0" encoding="utf-8"?>
<search>
<entry>
<title>闲暇时间的随手写</title>
<link href="/posts/e8b000e3.html"/>
<url>/posts/e8b000e3.html</url>
<content type="html"><![CDATA[<h1 id="2024-10-16"><a href="#2024-10-16" class="headerlink" title="2024/10/16"></a>2024/10/16</h1><h6 id="我们就是我们反复做的事情。"><a href="#我们就是我们反复做的事情。" class="headerlink" title="我们就是我们反复做的事情。"></a>我们就是我们反复做的事情。</h6><p>今天就算是一个开始吧，明天哔哩哔哩账户应该就6级了。</p><p>从七月初开始工作，至今已三个多月，工作的时间过得属实很快，不知不觉中就从指尖流淌而过，从周一到周五，和小学时期盼着周五快点到来一般。<br>但终究是不一样的，但说不出是何。</p><p>这篇随写起源于今早或是昨晚的一个兴起之念。这段时间想法越来越多，想表达的念头也愈发的多，断断续续，零零散散，以前总觉得这些是无意义的，记录起来也是枉然，回看也只是徒生尴尬。其实仔细想想，记录下来也是很好的。一些故事在记忆里愈发的模糊，就写在这里。</p><p>这一篇就这样吧。</p>]]></content>
<categories>
<category> 随记 </category>
<category> 碎碎念 </category>
</categories>
<tags>
<tag> 随记 </tag>
</tags>
</entry>
<entry>
<title>关于在WebPack以及NodeJs版本问题的一些坑</title>
<link href="/posts/a65f14fb.html"/>
<url>/posts/a65f14fb.html</url>
<content type="html"><![CDATA[<!-- markdownlint-disable MD025 --><h1 id="前言"><a href="#前言" class="headerlink" title="前言"></a>前言</h1><p>这是在一次更新NodeJs版本后项目出现的问题，具体为什么在最开始可以运行，后续出现依赖问题以及不得而知，<br>可能是因为更新了NodeJs版本，出现了不兼容问题，但是理论上来说，NodeJs的版本更新不会出现这种问题，<br>所以这里记录一下，以防以后再次出现这种问题。</p><h2 id="依赖问题描述"><a href="#依赖问题描述" class="headerlink" title="依赖问题描述"></a>依赖问题描述</h2><p>以及记不得最开始使用的NodeJs版本是多少了大概是16.20.0，然后更新到了18.16.0，然后就出现了问题，<br>在安装依赖的时候，会出现依赖安装失败问题，具体原因是html-webpack-plugin这个依赖我在这里使用的是5.5.0，<br>然后在安装的时候会出现这个问题，具体的错误信息如下：</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br></pre></td><td class="code"><pre><span class="line">npm ERR! code ERESOLVE</span><br><span class="line">npm ERR! ERESOLVE unable to resolve dependency tree</span><br><span class="line">npm ERR!</span><br><span class="line">npm ERR! While resolving: [email protected]</span><br><span class="line">npm ERR! Found: [email protected]</span><br><span class="line">npm ERR! node_modules/html-webpack-plugin</span><br><span class="line">npm ERR! dev html-webpack-plugin@<span class="string">"^5.5.1"</span> from the root project</span><br><span class="line">npm ERR!</span><br><span class="line">npm ERR! Could not resolve dependency:</span><br><span class="line">npm ERR! peer html-webpack-plugin@<span class="string">"^3.0.0 || ^4.0.0"</span> from [email protected]</span><br><span class="line">npm ERR! node_modules/script-ext-html-webpack-plugin</span><br><span class="line">npm ERR! dev script-ext-html-webpack-plugin@<span class="string">"2.1.5"</span> from the root project</span><br><span class="line">npm ERR!</span><br><span class="line">npm ERR! Fix the upstream dependency conflict, or retry</span><br><span class="line">npm ERR! this <span class="built_in">command</span> with --force or --legacy-peer-deps</span><br><span class="line">npm ERR! to accept an incorrect (and potentially broken) dependency resolution.</span><br></pre></td></tr></table></figure><p>这里的意思是说，html-webpack-plugin这个依赖的版本是5.5.3，需要使用的webpack版本是5，但是在script-ext-html-webpack-plugin这个依赖中，<br>需要的版本是3.0.0或者4.0.0，但是这里的版本是webpack5，所以如果要解决这个问题，需要将html-webpack-plugin这个依赖的版本降低到4及以下。</p><h2 id="运行问题描述"><a href="#运行问题描述" class="headerlink" title="运行问题描述"></a>运行问题描述</h2><p>由于之前更新了NodeJs版本，所以在运行的时候会出现一些问题，具体的错误信息如下：</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br></pre></td><td class="code"><pre><span class="line">node:internal/crypto/hash:71</span><br><span class="line"> this[kHandle] = new _Hash(algorithm, xofLen);</span><br><span class="line"> ^</span><br><span class="line"></span><br><span class="line">Error: error:0308010C:digital envelope routines::unsupported</span><br><span class="line"> at new Hash (node:internal/crypto/hash:71:19)</span><br><span class="line"> at Object.createHash (node:crypto:133:10)</span><br><span class="line"> at module.exports (C:\Users\Peridot\Escritorio\proyectos\DoneWithIt\node_modules\webpack\lib\util\createHash.js:135:53)</span><br><span class="line"> at NormalModule._initBuildHash (C:\Users\Peridot\Escritorio\proyectos\DoneWithIt\node_modules\webpack\lib\NormalModule.js:417:16)</span><br><span class="line"> at handleParseError (C:\Users\Peridot\Escritorio\proyectos\DoneWithIt\node_modules\webpack\lib\NormalModule.js:471:10)</span><br><span class="line"> at C:\Users\Peridot\Escritorio\proyectos\DoneWithIt\node_modules\webpack\lib\NormalModule.js:503:5</span><br><span class="line"> at C:\Users\Peridot\Escritorio\proyectos\DoneWithIt\node_modules\webpack\lib\NormalModule.js:358:12</span><br><span class="line"> at C:\Users\Peridot\Escritorio\proyectos\DoneWithIt\node_modules\loader-runner\lib\LoaderRunner.js:373:3</span><br><span class="line"> at iterateNormalLoaders (C:\Users\Peridot\Escritorio\proyectos\DoneWithIt\node_modules\loader-runner\lib\LoaderRunner.js:214:10)</span><br><span class="line"> at Array.<anonymous> (C:\Users\Peridot\Escritorio\proyectos\DoneWithIt\node_modules\loader-runner\lib\LoaderRunner.js:205:4)</span><br><span class="line"> at Storage.finished (C:\Users\Peridot\Escritorio\proyectos\DoneWithIt\node_modules\enhanced-resolve\lib\CachedInputFileSystem.js:55:16)</span><br><span class="line"> at C:\Users\Peridot\Escritorio\proyectos\DoneWithIt\node_modules\enhanced-resolve\lib\CachedInputFileSystem.js:91:9</span><br><span class="line"> at C:\Users\Peridot\Escritorio\proyectos\DoneWithIt\node_modules\graceful-fs\graceful-fs.js:123:16</span><br><span class="line"> at FSReqCallback.readFileAfterClose [as oncomplete] (node:internal/fs/read_file_context:68:3) {</span><br><span class="line"> opensslErrorStack: [ <span class="string">'error:03000086:digital envelope routines::initialization error'</span> ],</span><br><span class="line"> library: <span class="string">'digital envelope routines'</span>,</span><br><span class="line"> reason: <span class="string">'unsupported'</span>,</span><br><span class="line"> code: <span class="string">'ERR_OSSL_EVP_UNSUPPORTED'</span></span><br><span class="line">}</span><br><span class="line"></span><br><span class="line">Node.js v18.12.1</span><br></pre></td></tr></table></figure><p>在这里的错误信息中，可以看到，这里的错误信息是在crypto这个模块中出现的，具体的错误信息是说，这个模块中的hash方法出现了问题，<br>这个方法是用来加密的，但是在这里出现了不支持的错误，这个错误的原因是从NodeJs版本 17 开始，NodeJs从 OpenSSL1.1.1 升级到 OpenSSL3。OpenSSL3不支持一些旧的哈希技术。这就是为什么我们面临这个错误“ERR_OSSL_EVP_UNSUPPORTED”。如果不想降低NodeJs版本，我们就需要在终端在设置NodeJs需要使用的OpenSSL版本，具体的命令如下：</p><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"><span class="built_in">export</span> NODE_OPTIONS=--openssl-legacy-provider</span><br></pre></td></tr></table></figure><p>这样子，当我们再次运行的时候，就不会出现这个问题了。</p><h2 id="总结"><a href="#总结" class="headerlink" title="总结"></a>总结</h2><p>这个问题困扰了我很久很久，前端的项目依赖相对与Java来说要混乱很多，这也就是package-lock.json 的存在原因，避免随着依赖的变更导致项目无法运行。虽然新的版本会有更好的优化以及新功能，但是偶尔会废弃一些旧的功能，我们在新版本的环境是，可能就会出现不兼容问题了，所以在选择升级之前一定要搞清楚每一次的更新细节，更改了什么，废弃了什么，这样子才能避免一些不必要的问题。</p>]]></content>
<categories>
<category> 编程 </category>
<category> 前端 </category>
<category> Vue </category>
</categories>
<tags>
<tag> NodeJs </tag>
<tag> NPM </tag>
<tag> Vue </tag>
</tags>
</entry>
<entry>
<title>Linux 命令</title>
<link href="/posts/9da1ef6b.html"/>
<url>/posts/9da1ef6b.html</url>
<content type="html"><![CDATA[]]></content>
<categories>
<category> 随记 </category>
</categories>
<tags>
<tag> Linux </tag>
</tags>
</entry>
<entry>
<title>SpringBoot</title>
<link href="/posts/6f2612a2.html"/>
<url>/posts/6f2612a2.html</url>
<content type="html"><![CDATA[<p>关于文件上传</p><p>Html部分</p><figure class="highlight html"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta"><!DOCTYPE <span class="keyword">html</span>></span></span><br><span class="line"><span class="tag"><<span class="name">html</span> <span class="attr">lang</span>=<span class="string">"en"</span>></span></span><br><span class="line"><span class="tag"><<span class="name">head</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">meta</span> <span class="attr">charset</span>=<span class="string">"UTF-8"</span> <span class="attr">content</span>=<span class="string">"application/json"</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">title</span>></span>表单<span class="tag"></<span class="name">title</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">link</span> <span class="attr">rel</span>=<span class="string">"shortcut icon"</span> <span class="attr">th:href</span>=<span class="string">"@{/static/favicon.png}"</span>/></span></span><br><span class="line"><span class="tag"></<span class="name">head</span>></span></span><br><span class="line"><span class="tag"><<span class="name">script</span> <span class="attr">src</span>=<span class="string">"https://cdnjs.cloudflare.com/ajax/libs/jquery/3.6.1/jquery.min.js"</span>></span></span><br><span class="line"><span class="tag"></<span class="name">script</span>></span></span><br><span class="line"><span class="tag"><<span class="name">body</span>></span></span><br><span class="line"><span class="tag"><<span class="name">div</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">form</span> <span class="attr">id</span>=<span class="string">"uploadImage"</span> <span class="attr">action</span>=<span class="string">"http://localhost:8080/upData"</span> <span class="attr">method</span>=<span class="string">"post"</span> <span class="attr">enctype</span>=<span class="string">"multipart/form-data"</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">label</span>></span></span><br><span class="line"> Images</span><br><span class="line"> <span class="tag"><<span class="name">input</span> <span class="attr">id</span>=<span class="string">"image"</span> <span class="attr">name</span>=<span class="string">"file"</span> <span class="attr">type</span>=<span class="string">"file"</span> <span class="attr">accept</span>=<span class="string">"image/gif, image/jpg, image/png"</span>/></span></span><br><span class="line"> <span class="tag"></<span class="name">label</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">input</span> <span class="attr">type</span>=<span class="string">"submit"</span> <span class="attr">value</span>=<span class="string">"提交图片"</span>/></span></span><br><span class="line"> <span class="tag"></<span class="name">form</span>></span></span><br><span class="line"><span class="tag"></<span class="name">div</span>></span></span><br><span class="line"><span class="comment"><!-- 用于实时显示用户上传图片，提供及时反馈 --></span></span><br><span class="line"><span class="tag"><<span class="name">img</span> <span class="attr">id</span>=<span class="string">"images"</span> <span class="attr">src</span>=<span class="string">""</span> <span class="attr">alt</span>=<span class="string">""</span> <span class="attr">style</span>=<span class="string">"width: 100px;height: 100px;visibility: collapse"</span>></span></span><br><span class="line"><span class="tag"></<span class="name">body</span>></span></span><br><span class="line"><span class="tag"></<span class="name">html</span>></span></span><br></pre></td></tr></table></figure><p>这里的enctype很重要<br>官方解释：</p><figure class="highlight text"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line">enctype：</span><br><span class="line">如果method属性的值为post ，则enctype是表单提交的MIME 类型 。可能的值：</span><br><span class="line">application/x-www-form-urlencoded ：默认值。</span><br><span class="line">multipart/form-data ：如果表单包含type=file的<input>元素，则使用此选项。</span><br><span class="line">text/plain ：由 HTML5 引入，用于调试目的。</span><br><span class="line">该值可以被<button> 、 <input type="submit"> 或<input type="image"> 元素上的formenctype属性覆盖。</span><br></pre></td></tr></table></figure><p>当我们提交的是带有文件的提交时，我们就需要使用multipart/form-data</p><p>后端继承自SpringBoot<br>代码如下：<br>这里上传的文件会存储在项目同级目录下的static下</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@CrossOrigin</span></span><br><span class="line"><span class="meta">@PostMapping("/upData")</span></span><br><span class="line"><span class="keyword">public</span> String <span class="title function_">upload</span><span class="params">(<span class="meta">@RequestParam("file")</span> MultipartFile file)</span> <span class="keyword">throws</span> IOException {</span><br><span class="line"> <span class="type">String</span> <span class="variable">originalFilename</span> <span class="operator">=</span> file.getOriginalFilename();</span><br><span class="line"> <span class="type">String</span> <span class="variable">FileType</span> <span class="operator">=</span> originalFilename.substring(originalFilename.lastIndexOf(<span class="string">"."</span>));</span><br><span class="line"> <span class="type">String</span> <span class="variable">NewFileName</span> <span class="operator">=</span> UUID.randomUUID() + FileType;</span><br><span class="line"> <span class="type">String</span> <span class="variable">dir</span> <span class="operator">=</span> ResourceUtils.getURL(<span class="string">"classpath:"</span>).getPath();</span><br><span class="line"> String[] targets = dir.split(<span class="string">"target"</span>);</span><br><span class="line"> String[] split = targets[<span class="number">0</span>].split(<span class="string">"file:/"</span>);</span><br><span class="line"> <span class="type">String</span> <span class="variable">newDir</span> <span class="operator">=</span> split[<span class="number">1</span>];</span><br><span class="line"> <span class="type">String</span> <span class="variable">decode</span> <span class="operator">=</span> URLDecoder.decode(newDir, <span class="string">"utf-8"</span>);</span><br><span class="line"> <span class="type">File</span> <span class="variable">Path</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">File</span>(decode + <span class="string">"/static/"</span> + NewFileName);</span><br><span class="line"> System.out.println(Path.getPath());</span><br><span class="line"> <span class="keyword">if</span> (!Path.exists()) {</span><br><span class="line"> Path.mkdirs();</span><br><span class="line"> }</span><br><span class="line"> file.transferTo(Path);</span><br><span class="line"> System.out.println(<span class="string">"上传成功"</span>);</span><br><span class="line"> <span class="keyword">return</span> <span class="string">"Success"</span>+Path.getPath();</span><br><span class="line">}</span><br></pre></td></tr></table></figure>]]></content>
<categories>
<category> SpringBoot UpLoad </category>
</categories>
<tags>
<tag> SpringBoot Html </tag>
</tags>
</entry>
<entry>
<title>Git小知识</title>
<link href="/posts/9b0be8b0.html"/>
<url>/posts/9b0be8b0.html</url>
<content type="html"><![CDATA[<p>初始化git仓库</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">git init</span><br></pre></td></tr></table></figure><p>已经有远程仓库，想要clone到本地<br>lone 的仓库不需要进行上下游链接</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">git clone <Repository_link></span><br></pre></td></tr></table></figure><p>不clone 链接远程仓库</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">git remote add <Repository_link></span><br></pre></td></tr></table></figure><p>创建分支</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">git branch <branch name></span><br></pre></td></tr></table></figure><p>切换分支</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">git checkout <branch name></span><br></pre></td></tr></table></figure><p>删除本地分支 ： 如分支名为dev</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">git branch -D dev</span><br><span class="line">它会直接删除,不检查</span><br></pre></td></tr></table></figure><p>创建远程分支</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">git push origin <branch Name></span><br></pre></td></tr></table></figure><p>创建远程分支后要记得进行上下游链接</p><p>设置上游远程分支<br>方式一（适用远程分支已存在）：<br>用参数 -u 或 —set-upstream-to 设置上游</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">git branch --set-upstream-to=origin/<远程分支> <本地分支></span><br></pre></td></tr></table></figure><p>方式二（适用远程分支不存在）：</p><p>上传本地分支到远程，同是把上传后的远程分支设置为本地分支的上游分支：</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">git push set-upstream origin HEAD:<远程分支></span><br></pre></td></tr></table></figure><p> 取消分支上游：</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">git branch --unset-upstream</span><br></pre></td></tr></table></figure><p>删除远程分支</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">git push origin -d dev</span><br></pre></td></tr></table></figure><p>查看上游：<br>可以通过git status 、 git checkout <分支>、git branch -vv命令查看</p><p>清理本地不存在的远程分支，如别人删除了dev,但是你本地查看还有，就可以执行该条命令</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">git remote prune origin</span><br></pre></td></tr></table></figure><p>合并分支</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">git merge [merge-Branch-Name]</span><br></pre></td></tr></table></figure><p>合并之后，我们应该就不再需要这个分支了，可以删除</p><p>合并冲突<br>如果git此时无法自动进行合并操作，我们可以在任意时刻使用git status命令查看那些因为包含合并冲突而处于未合并状态的文件</p><p>任何因包含合并冲突而有待解决的文件，都会以未合并状态标识出来。 Git 会在有冲突的文件中加入标准的冲突解决标记，这样你可以打开这些包含冲突的文件然后手动解决冲突。 出现冲突的文件会包含一些特殊区段，看起来像下面这个样子：</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><<<<<<< HEAD:index.html</span><br><span class="line"><div id="footer">contact : [email protected]</div></span><br><span class="line">=======</span><br><span class="line"><div id="footer"></span><br><span class="line"> please contact us at [email protected]</span><br><span class="line"></div></span><br><span class="line">>>>>>>> iss53:index.html</span><br></pre></td></tr></table></figure><p>这表示 HEAD 所指示的版本（也就是你的 master 分支所在的位置，因为你在运行 merge 命令的时候已经检出到了这个分支）在这个区段的上半部分（======= 的上半部分），而 iss53 分支所指示的版本在 ======= 的下半部分。 为了解决冲突，你必须选择使用由 ======= 分割的两部分中的一个，或者你也可以自行合并这些内容。 例如，你可以通过把这段内容换成下面的样子来解决冲突：</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><div id="footer"></span><br><span class="line">please contact us at [email protected]</span><br><span class="line"></div></span><br></pre></td></tr></table></figure><p>上述的冲突解决方案仅保留了其中一个分支的修改，并且 <<<<<<< , ======= , 和 >>>>>>> 这些行被完全删除了。 在你解决了所有文件里的冲突之后，对每个文件使用 git add 命令来将其标记为冲突已解决。 一旦暂存这些原本有冲突的文件，Git 就会将它们标记为冲突已解决。</p><p>如果你对结果感到满意，并且确定之前有冲突的的文件都已经暂存了，这时你可以输入 git commit 来完成合并提交。 默认情况下提交信息看起来像下面这个样子：</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br></pre></td><td class="code"><pre><span class="line">Merge branch 'iss53'</span><br><span class="line"></span><br><span class="line">Conflicts:</span><br><span class="line"> index.html</span><br><span class="line">#</span><br><span class="line"># It looks like you may be committing a merge.</span><br><span class="line"># If this is not correct, please remove the file</span><br><span class="line"># .git/MERGE_HEAD</span><br><span class="line"># and try again.</span><br><span class="line"></span><br><span class="line"></span><br><span class="line"># Please enter the commit message for your changes. Lines starting</span><br><span class="line"># with '#' will be ignored, and an empty message aborts the commit.</span><br><span class="line"># On branch master</span><br><span class="line"># All conflicts fixed but you are still merging.</span><br><span class="line">#</span><br><span class="line"># Changes to be committed:</span><br><span class="line"># modified: index.html</span><br><span class="line">#</span><br></pre></td></tr></table></figure><p>变基</p><p>提取在 C4 中引入的补丁和修改，然后在 C3 的基础上应用一次。 在 Git 中，这种操作就叫做 变基（rebase）你可以使用 rebase 命令将提交到某一分支上的所有修改都移至另一分支上，就好像“重新播放”一样。</p><p>关于撤销操作<br>如果我们在提交之后突然发现少提交的了一些东西，或者想修改提交信息，我们可以使用 带< —amend > 参数的commit重复提交</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">git commit -m "You Commit Message"</span><br><span class="line">git add xxxxx</span><br><span class="line">git commit --amend</span><br></pre></td></tr></table></figure><p>最终你只会有一个提交——第二次提交将代替第一次提交的结果。</p><p>取消暂存区文件</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">git reset <file name 如果指定文件 则指定取消暂存文件，否则取消当前分支的全部文件暂存></span><br></pre></td></tr></table></figure><p>撤销对文件的修改<br>其实< git status 告诉了我们可能使用什么命令></p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">git checkout -- files/file name</span><br></pre></td></tr></table></figure><p>标签<br>有时候我们需要给某个版本打上特定的标记/标签，我们可以使用</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">git tag tag-name</span><br></pre></td></tr></table></figure><p>推送标签</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">git push --tags</span><br></pre></td></tr></table></figure>]]></content>
<categories>
<category> Git </category>
</categories>
<tags>
<tag> Git </tag>
</tags>
</entry>
<entry>
<title>Git</title>
<link href="/posts/69c3279c.html"/>
<url>/posts/69c3279c.html</url>
<content type="html"><![CDATA[<!-- markdownlint-disable MD025 --><h1 id="序"><a href="#序" class="headerlink" title="序"></a>序</h1>]]></content>
<categories>
<category> Git </category>
</categories>
<tags>
<tag> Git </tag>
</tags>
</entry>
<entry>
<title>Android布局</title>
<link href="/posts/a9a74215.html"/>
<url>/posts/a9a74215.html</url>
<content type="html"><![CDATA[<!-- markdownlint-disable MD025 --><h1 id="Android-布局"><a href="#Android-布局" class="headerlink" title="Android 布局"></a>Android 布局</h1><h2 id="五种基础布局"><a href="#五种基础布局" class="headerlink" title="五种基础布局"></a>五种基础布局</h2><h3 id="1、LinearLayout-（线性布局）"><a href="#1、LinearLayout-（线性布局）" class="headerlink" title="1、LinearLayout （线性布局）"></a>1、LinearLayout （线性布局）</h3><blockquote><p>LinearLayout是一种线型的布局方式。LinearLayout布局容器内的组件一个挨着一个地排列起来：不仅可以控制个组件横向排列，也可控制各组件纵向排列。</p></blockquote><ul><li>android:orientation 属性指定了排列方向,可以选择vertical与horizontal</li><li>android:gravity 属性制定了文字在控件中的对齐方式，与HTML对齐方式大致相同</li><li>android:layout_gravity 属性和上面的属性看起来很像，但是多了一个layout前缀，因此他可以指定控件在布局中的对齐方式</li><li>android:layout_weight=”1”(权重),weight处于垂直布局时代表行距，水平布局时代表列宽，weight值越大则对应的行距或列宽越大</li><li>android:visibility=invisible控制布局是否显示 1、visible 显示 2、invisible 不显示但依旧占用布局空间 3、gone 隐藏控件</li></ul><h3 id="2、RelativeLayout（相对布局）"><a href="#2、RelativeLayout（相对布局）" class="headerlink" title="2、RelativeLayout（相对布局）"></a>2、RelativeLayout（相对布局）</h3><p>后续更新</p><h3 id="3、FrameLayout（帧布局）"><a href="#3、FrameLayout（帧布局）" class="headerlink" title="3、FrameLayout（帧布局）"></a>3、FrameLayout（帧布局）</h3><p>后续更新</p><h3 id="4、TableLayout（表格布局）GridLayout-网格布局"><a href="#4、TableLayout（表格布局）GridLayout-网格布局" class="headerlink" title="4、TableLayout（表格布局）GridLayout 网格布局"></a>4、TableLayout（表格布局）GridLayout 网格布局</h3><p>后续更新</p><h3 id="5、AbsoluteLayout（绝对布局）"><a href="#5、AbsoluteLayout（绝对布局）" class="headerlink" title="5、AbsoluteLayout（绝对布局）"></a>5、AbsoluteLayout（绝对布局）</h3><p>后续更新</p>]]></content>
<categories>
<category> 编程 </category>
<category> Android </category>
</categories>
<tags>
<tag> Android </tag>
<tag> 布局 </tag>
</tags>
</entry>
<entry>
<title>Android核心组件</title>
<link href="/posts/9490d20a.html"/>
<url>/posts/9490d20a.html</url>
<content type="html"><![CDATA[<!-- markdownlint-disable MD025 --><h1 id="Android四大组件分别为Activity、Service、Content-Provider、Broadcast-Receiver"><a href="#Android四大组件分别为Activity、Service、Content-Provider、Broadcast-Receiver" class="headerlink" title="Android四大组件分别为Activity、Service、Content Provider、Broadcast Receiver"></a>Android四大组件分别为Activity、Service、Content Provider、Broadcast Receiver</h1><h2 id="一、Activity组件"><a href="#一、Activity组件" class="headerlink" title="一、Activity组件"></a>一、Activity组件</h2><p>Activity的主要的作用就是一个Activity通常就是一个活动窗口，交互的载体。</p><p>一个Activity通常就是一个单独的屏幕（窗口）。<br>Activity之间通过Intent进行通信。<br>每一个Activity都必须要在AndroidManifest.xml配置文件中声明，否则系统将不识别也不执行该Activity。</p><h2 id="二、Service-服务"><a href="#二、Service-服务" class="headerlink" title="二、Service 服务"></a>二、Service 服务</h2><p>与Activity具备一个前台显示界面的活动组件不同，Android中有一个组件，没有显示画面，一般不需要与用户进行交互，该组件通常运行在后台，称之为Service服务组件。</p><p>如果想要实现自己自定义的Service，需要继承自系统的Service基类，同样也需要在清单文件AndroidMainfest.xml文件中进行声明。关于Service，可以简单总结如下：</p><p>Service通常用于在后台完成用户指定的操作。<br>Service也同样有生命周期，可以进行声明周期的管理。<br>Service分为两类：startService和bindService。<br>自定义实现的Service需要在清单配置文件中进行声明和注册。<br>startService<br>在其他组件（比如Activity）中通过startService启动一个后台服务组件，服务启动后，服务的生命周期和活动状态和启动该服务的组件不再有关系，即该服务的运行状态变得独立。</p><p>bindService<br>与startService方式启动的服务不同，如果是通过bindService启动某个服务组件，则意味着启动服务的组件和服务进行了绑定，存在一种绑定关系。如果某个时刻，调用者（比如说Activity）触法退出逻辑，关闭活动页面，则通过bindService绑定的服务也会随机停止。类似于“不求同年同月同日生生，但求同年同月同日生死”的悲壮。</p><h2 id="三、ContentProvider内容提供者"><a href="#三、ContentProvider内容提供者" class="headerlink" title="三、ContentProvider内容提供者"></a>三、ContentProvider内容提供者</h2><p>ContentProvider 通常被直译为内容提供者，组件名字很形象的诠释了该组件的作用。在Android系统中，每个应用程序是运行在不同的进程中，进程间是相互独立的。如果开发者开发的某一个应用程序，需要提供一些数据给其他应用程序，则可以通过ContentProvider将提供的数据进行暴露，其他应用程序通过ContentResolver从内容提供者中获取相应的数据。对Content Provider相关的内容进行总结：</p><p>A应用程序使用Content Provider提供共享数据，B应用程序通过Content Resolver按照规则获取数据。<br>只有需要在多个应用程序间共享数据时才需要内容提供者。例如，通讯录数据被多个应用程序使用，且必须存储在一个内容提供者中。它的好处是统一数据访问方式。<br>ContentProvider实现数据共享。<br>ContentProvider使用URI来唯一标识其数据集，这里的URI以content://作为前缀，表示该数据由ContentProvider来管理。<br>需要在清单配置文件中进行注册和声明。<br>四、Boradcast Receiver广播接受者<br>Android中的广播的工作方式类似于隐式Intent的工作方式，开发者可以指定接收一些事件，该事件既可以是自定义的，也可以是系统定义的。在程序运行时，可以根据指定的事件进行过滤和拦截，符合要求的事件，会被广播接收器接收，并执行相应的业务逻辑。Android系统中广播接收者的出现，实现了极大的模块的解耦。</p><p>对于广播接收者，总结如下：</p><p>广播接收者可以通过事件过滤和拦截，实现组件的通信。<br>广播接收者的注册有两种方式：动态注册（代码中注册）和静态注册（清单文件注册）。<br>动态注册：Activity关闭后，失效。静态注册：不会失效。</p>]]></content>
<categories>
<category> 编程 </category>
<category> Android </category>
</categories>
<tags>
<tag> Android </tag>
<tag> 组件 </tag>
</tags>
</entry>
<entry>
<title>Java JNA的使用</title>
<link href="/posts/45e49ef2.html"/>
<url>/posts/45e49ef2.html</url>
<content type="html"><![CDATA[<!-- markdownlint-disable MD025 --><h1 id="Java-JNA"><a href="#Java-JNA" class="headerlink" title="Java JNA"></a>Java JNA</h1><h2 id="简介"><a href="#简介" class="headerlink" title="简介"></a>简介</h2><p>JNA 全称‘Java Native Access’ 是一个建立在传统JNI技术上的Java开源框架。JNA提供了一组Java工具类用于运行期动态访问系统本地库（Native Library）而不需要编写任何Native、JNI代码。开发者只需要在Java接口中描述目标Native Library的函数与结构，JNA会自动实现Java接口到Native Function的映射。</p><p>1，dll和so是C函数的集合和容器，这与Java中的接口概念吻合，所以JNA把dll文件和so文件看成一个个接口。在JNA中定义一个接口就是相当于了定义一个DLL/SO文件的描述文件，该接口代表了动态链接库中发布的所有函数。而且，对于程序不需要的函数，可以不在接口中声明。</p><p>2，JNA定义的接口一般继承com.sun.jna.Library接口，如果dll文件中的函数是以stdcall方式输出函数，那么，该接口就应该继承com.sun.jna.win32.StdCallLibrary接口。</p><p>3，Jna难点：编程语言之间的数据类型不一致。</p><h2 id="类型对照"><a href="#类型对照" class="headerlink" title="类型对照"></a>类型对照</h2><div class="table-container"><table><thead><tr><th>Java类型</th><th>C类型</th><th>C类型原生表现</th></tr></thead><tbody><tr><td>boolean</td><td>int</td><td>32位整数(可定制)</td></tr><tr><td>byte</td><td>char</td><td>8位整数</td></tr><tr><td>char</td><td>wchar_t</td><td>平台依赖</td></tr><tr><td>short</td><td>short</td><td>16位整数</td></tr><tr><td>int</td><td>int</td><td>32位整数</td></tr><tr><td>long</td><td>long,__int64</td><td>64位整数</td></tr><tr><td>float</td><td>float</td><td>32位浮点数</td></tr><tr><td>double</td><td>double</td><td>64位浮点数</td></tr><tr><td>Buffer/Pointer</td><td>pointer</td><td>平台依赖(32或64位指针)</td></tr><tr><td></td><td>pointer/array</td><td>32或64位指针(参数/返回值)邻接内存(结构体成员)</td></tr><tr><td>String</td><td>char*</td><td>/0结束的数组(nativeencodingorjna.encoding)</td></tr><tr><td>WString</td><td>wchar_t*</td><td>/0结束的数组(unicode)</td></tr><tr><td>String[]</td><td>char**</td><td>/0结束的数组的数组</td></tr><tr><td>WString[]</td><td>wchar_t**</td><td>/0结束的宽字符数组的数组</td></tr><tr><td>Structure</td><td>struct*/struct</td><td>指向结构体的指针(参数或返回值)(或者明确指定是结构体指针)结构体(结构体的成员)(或者明确指定是结构体)</td></tr><tr><td>Union</td><td>union</td><td>等同于结构体</td></tr><tr><td>Structure[]</td><td>struct[]</td><td>结构体的数组，邻接内存</td></tr><tr><td>Callback</td><td>(*fp)()</td><td>Java函数指针或原生函数指针</td></tr><tr><td>NativeMapped</td><td>varies</td><td>依赖于定义</td></tr><tr><td>NativeLong</td><td>long</td><td>平台依赖(32或64位整数)</td></tr><tr><td>PointerType</td><td>pointer</td><td>和Pointer相同</td></tr></tbody></table></div><h2 id="案例"><a href="#案例" class="headerlink" title="案例"></a>案例</h2><p>下面的示例映射了标准C库中的printf函数并调用。</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.sun.jna.examples;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> com.sun.jna.Library;</span><br><span class="line"><span class="keyword">import</span> com.sun.jna.Native;</span><br><span class="line"><span class="keyword">import</span> com.sun.jna.Platform;</span><br><span class="line"></span><br><span class="line"><span class="comment">/** JNA简单接口示例 */</span></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">HelloWorld</span> {</span><br><span class="line"></span><br><span class="line"> <span class="comment">// 这是标准的，稳定的映射方式，支持广泛</span></span><br><span class="line"> <span class="comment">// Java类型到Native类型的定制和映射</span></span><br><span class="line"></span><br><span class="line"> <span class="keyword">public</span> <span class="keyword">interface</span> <span class="title class_">CLibrary</span> <span class="keyword">extends</span> <span class="title class_">Library</span> {</span><br><span class="line"> <span class="type">CLibrary</span> <span class="variable">INSTANCE</span> <span class="operator">=</span> (CLibrary)Native.load((Platform.isWindows() ? <span class="string">"msvcrt"</span> : <span class="string">"c"</span>),CLibrary.class);</span><br><span class="line"> <span class="keyword">void</span> <span class="title function_">printf</span><span class="params">(String format, Object... args)</span>;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> {</span><br><span class="line"> CLibrary.INSTANCE.printf(<span class="string">"Hello, World\n"</span>);</span><br><span class="line"> <span class="keyword">for</span> (<span class="type">int</span> i=<span class="number">0</span>;i < args.length;i++) {</span><br><span class="line"> CLibrary.INSTANCE.printf(<span class="string">"Argument %d: %s\n"</span>, i, args[i]);</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p>运行程序，如果不带参数就会单独打印“Hello，World”，如果带参则会打印出所有参数。由此可以看出，不需要写一行C代码，就可以直接在Java中调用外部动态链接库里的函数。<br>注意：参照上面的类型对照表，可以发现，传参不支持Class。</p><h3 id="关于C输出语句占位符"><a href="#关于C输出语句占位符" class="headerlink" title="关于C输出语句占位符"></a>关于C输出语句占位符</h3><div class="table-container"><table><thead><tr><th>格式</th><th>含义</th></tr></thead><tbody><tr><td>%d, %i</td><td>代表整数</td></tr><tr><td>%f</td><td>浮点</td></tr><tr><td>%s</td><td>字符串</td></tr><tr><td>%c</td><td>char</td></tr><tr><td>%p</td><td>指针</td></tr><tr><td>%fL</td><td>长log</td></tr><tr><td>%e</td><td>科学计数</td></tr><tr><td>%g</td><td>小数或科学计数。</td></tr><tr><td>%a,%A</td><td>读入一个浮点值(仅C99有效)。</td></tr><tr><td>%c</td><td>读入一个字符。</td></tr><tr><td>%d</td><td>读入十进制整数。</td></tr><tr><td>%i</td><td>读入十进制，八进制，十六进制整数。</td></tr><tr><td>%o</td><td>读入八进制整数。</td></tr><tr><td>%x,</td><td>%X 读入十六进制整数。</td></tr><tr><td>%s</td><td>读入一个字符串，遇空格、制表符或换行符结束。</td></tr><tr><td>%f,%F,%e,%E,%g,%G</td><td>用来输入实数，可以用小数形式或指数形式输入。</td></tr><tr><td>%p</td><td>读入一个指针。</td></tr><tr><td>%u</td><td>读入一个无符号十进制整数。</td></tr><tr><td>%n</td><td>至此已读入值的等价字符数。</td></tr><tr><td>%[]</td><td>扫描字符集合。</td></tr><tr><td>%%</td><td>读 % 符号</td></tr></tbody></table></div><h3 id="程序解读"><a href="#程序解读" class="headerlink" title="程序解读"></a>程序解读</h3><p>1、首先定义一个接口用于Native Function映射，继承自Library或StdCallLibrary<br>默认继承Library，如果dll中的函数是以stdcall方式调用，那么就继承StdCallLibrary，WIN32 Api都采用stdcall调用方式 就例如Windows中最为重要的kernel32库</p><p>2、接口内部定义<br>接口内部需要一个公共的静态常量：INSTANCE，通过这个常量我们可以获得这个接口的实例，从而使用接口的方法，也就是最关键的，调用外部dll/so的函数。该常量通过Native.load()静态函数获得，该函数的弃用方法为 <strong>Native.loadLibrary()</strong> 该函数有两个参数：</p><ul><li><p>第一个参数是动态链接库dll/so的名称，但不带.dll或.so这样的后缀，这符合JNI的规范，因为带了后缀名就不可以跨操作系统平台了。搜索动态链接库路径的顺序是：先从当前类的当前文件夹找，如果没有找到，再在工程当前文件夹下面找win32/win64文件夹，找到后搜索对应的dll文件，如果找不到再到WINDOWS下面去搜索，再找不到就会抛异常了。比如上例中printf函数在Windows平台下所在的dll库名称是msvcrt，而在其它平台如Linux下的so库名称是c。</p></li><li><p>第二个参数是本接口的Class类型。JNA通过这个Class类型，根据指定的.dll/.so文件，动态创建接口的实例。该实例由JNA通过反射自动生成。</p></li></ul><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"><span class="type">CLibrary</span> <span class="variable">getInstance</span> <span class="operator">=</span> (CLibrary) Native.load(Platform.isWindows() ? <span class="string">"msvcrt"</span> : <span class="string">"c"</span>, CLibrary.class);</span><br></pre></td></tr></table></figure><p>接口中只需要定义你要用到的函数或公共变量，不需要的可以不定义，如上面的例子之定义了printf函数</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">void</span> <span class="title function_">printf</span><span class="params">(String from, Object... args)</span>;</span><br></pre></td></tr></table></figure><p>定义的时候要注意参数和返回值的类型，需要同链接库中的函数类型保持一致</p><p>3、调用dll函数<br>定义好接口之后，我们就可以使用接口方法调用dll/so中相对应的函数了。</p><p>如果想调用自己实现的库函数，可以将自己实现的库函数编译成dll/so，放到当前目录下，然后和上述例子一样的去编写调用即可。</p><p>关于Windows下dll的函数导出列表可以自行查询。这里有一个网站记载了了Windows的所有<a href="http://windows10dll.nirsoft.net">dll</a></p><h2 id="JNA构造结构体"><a href="#JNA构造结构体" class="headerlink" title="JNA构造结构体"></a>JNA构造结构体</h2><p>在C里面没有Class类型，但是我们需要传递对象时可以通过转化为Struct</p>]]></content>
<categories>
<category> 编程 </category>
<category> Java </category>
</categories>
<tags>
<tag> JNA </tag>
<tag> Java </tag>
</tags>
</entry>
<entry>
<title>软件测试</title>
<link href="/posts/7a8ab919.html"/>
<url>/posts/7a8ab919.html</url>
<content type="html"><![CDATA[<!-- markdownlint-disable MD025 --><h1 id="软件测试"><a href="#软件测试" class="headerlink" title="软件测试"></a>软件测试</h1><h2 id="简介"><a href="#简介" class="headerlink" title="简介"></a>简介</h2><h3 id="生命周期"><a href="#生命周期" class="headerlink" title="生命周期"></a>生命周期</h3><p>每一个产品都具有一个生命周期，从需求阶段——>设计阶段——>开发阶段——>测试阶段——>维护阶段——>死亡阶段</p><h4 id="需求阶段"><a href="#需求阶段" class="headerlink" title="需求阶段"></a>需求阶段</h4><p>这是整个软件开发生命周期中最关键的阶段，在这个阶段，客户需要说明需求、规格、期望以及一些与产品相关的特殊要求。在这个阶段收集到的所有信息对于产品是否符合需求至关重要。</p><h4 id="设计阶段"><a href="#设计阶段" class="headerlink" title="设计阶段"></a>设计阶段</h4><p>设计阶段包括了根据需求阶段对新软件的详细分析。这是系统开发生命周期中的最高优先级阶段，因为系统的逻辑设计需要转化为物理设计。所需阶段的输出是需求事务的集合，设计阶段为实现这些需求提供了方法，所有必须的基本工具的决定，例如编程语言的选择、数据库的选择、硬件的选择、架构的选择，提供了一个平台。软件软件可以在这个平台上运行而没有任何问题。使用生命技术和工具，如数据流图、流程图、决策表。决策树、数据字典和结构化字典用于描述系统设计。</p><h4 id="开发阶段"><a href="#开发阶段" class="headerlink" title="开发阶段"></a>开发阶段</h4><p>在完成需求和设计阶段后，就会将设计实现到软件系统的具体开发中。在这个个阶段，工作可能会划分为一个个小单元，编码由开发人员根据前一阶段讨论的设计开始，并根据需求阶段的要求产生需求结果。前端开发人员开发简单且由吸引力的GUI和必要的接口，以便与后端操作进行交互，后端开发人员根据功能需求进行后端编码。</p><h4 id="测试阶段"><a href="#测试阶段" class="headerlink" title="测试阶段"></a>测试阶段</h4><p>测试是完成软件系统的最后一步，在这里，我们将根据需求阶段中的要求对其进行测试。确认软件是否实际的符合需求。制定测试计划以开始测试，这个测试包含了所有的测试类型。如果测试过程中软件没有按照预期工作，那么就需要向开发提供有关该问题的信息，如果这是一个有效的缺陷或者值得修复，<br>那么它将会被修复，将其替换为新的，对此还需要进行验证测试。</p><h4 id="部署阶段"><a href="#部署阶段" class="headerlink" title="部署阶段"></a>部署阶段</h4><p>当软件测试完成且结果符合预期，并且软件工作中没有余留问题，就可以将他进行交付使用。当客户收到产品时，建议他们优先进行β测试，在β测试中，客户可以要求软件中没有但在需求文档中或其他任何GUI更改中提及的任何更改，以使其更加用户友好。除此之外，如果客户在使用该软件的过程中遇见任何类型的缺陷，它将会通知该软件的开发团队解决问题，如果这是一个严重的问题，那么开发团队需要在短时间内解决问题，如果这是一个不那么严重的问题，那它将会被留置到下个版本，在解决了所有类型的错误和变更后，软件将会被部署到最终用户。</p><h4 id="维护阶段"><a href="#维护阶段" class="headerlink" title="维护阶段"></a>维护阶段</h4><p>维护阶段是SDLC的最后和持久阶段，因为它是一直持续到软件生命周期结束的过程。当客户开始使用软件时，实际问题就已经开始产生，那时需要解决这些问题。这个阶段包含了对硬件以及软件进行更改以维持其运营效率，例如提高性能，增强安全功能以及更具客户的要求和即将到来的时间。这个不时处理产品的过程称之为维护。<br>所有这些都是软件开发生命周期(SDLC)的六个阶段，在这个阶段，软件开发过程发生。所有这些都是强制阶段，没有任何一个开发是不可能的，因为开发在软件的生命周期中持续进行维护”。</p><h4 id="需求分析"><a href="#需求分析" class="headerlink" title="需求分析"></a>需求分析</h4><p>手动测试程序的第一步是需求分析。在此阶段，测试人员分析SDLC(软件开发生命周期)的需求文档，以检查客户所述的要求。在检查要求后，测试人员制定测试计划以检查软件是否满足要求。</p><ul><li>进入条件 - 对于测试计划需求规范的规划，应该提供应用程序体系结构文档和明确定义的验收标准。</li><li>活动行为 - 准备所有要求和查询的列表，并从技术经理/主管，系统架构，业务分析师和客户处获得解决。列出要执行的所有类型的测试(性能，功能和安全性)。列出测试环境详细信息，其中应包含执行测试用例的所有必要工具。</li><li>交付成果 - 列出可测试要求和测试环境详细信息的所有必要测试。</li></ul><h4 id="测试计划"><a href="#测试计划" class="headerlink" title="测试计划"></a>测试计划</h4><p>创建测试计划的创建是STLC的关键阶段，它定义了所有测试策略。测试人员确定整个项目的估计工作量和成本。此阶段在成功完成需求分析阶段后进行。此阶段提供的测试策略和工作量估算文档。成功完成测试计划创建后，可以开始测试用例执行。</p><ul><li>进入条件 - 需求文档活动行为 - 定义目标以及软件的范围。列出测试中涉及的方法。测试过程概述。</li><li>测试环境的解决。准备测试计划和控制程序。角色和责任的确定。列出测试可交付成果，定义风险(如果有)。</li><li>交付成果 - 测试策略文档。测试估算文件是此阶段的交付成果。</li></ul><h4 id="环境设置"><a href="#环境设置" class="headerlink" title="环境设置"></a>环境设置</h4><p>测试环境的设置是一项独立的活动，可以与测试用例开发一起启动。这是手动测试程序的重要部分，因为没有环境测试无法进行。环境设置需要一组必要的软件和硬件来创建测试环境。测试团队不参与设置测试环境，而是创建测试环境的高级开发人员完成。</p><ul><li>进入条件 - 测试策略和测试计划文档。测试用例文档。测试数据。</li><li>活动行为 - 通过分析需求规范来准备软件和硬件列表。在设置测试环境之后，执行测试用例以检查测试环境的准备情况。</li><li>交付成果 - 执行报告。缺陷报告。</li></ul><h4 id="测试用例"><a href="#测试用例" class="headerlink" title="测试用例"></a>测试用例</h4><p>执行测试用例在成功完成测试计划后执行。在此阶段，测试团队启动案例开发和执行活动。测试团队记下详细的测试用例，并在需要时准备测试数据。准备好的测试用例由团队的同行成员或质量保证负责人进行审核。 RTM(需求可追溯性矩阵)也在此阶段准备。需求可跟踪性矩阵是行业级格式，用于跟踪需求。每个测试用例都与需求规范一起映射。可以通过RTM完成向后和向前可追溯性。</p><ul><li>进入条件 - 需求文档。</li><li>活动行为 - 创建测试用例。执行测试用例。根据要求绘制测试用例。</li><li>交付成果 - 测试执行结果。具有缺陷详细说明的功能列表。</li></ul><h4 id="缺陷记录"><a href="#缺陷记录" class="headerlink" title="缺陷记录"></a>缺陷记录</h4><p>测试人员和开发人员根据测试覆盖范围，质量，时间消耗，成本和关键业务目标评估软件的完成标准。此阶段确定了软件的特性和缺点。深入分析测试用例和错误报告，以检测缺陷的类型及其严重性。 缺陷记录分析主要用于根据严重程度和类型找出缺陷分布。如果检测到任何缺陷，则将软件返回给开发团队以修复缺陷，然后在测试的所有方面对软件进行重新测试。 一旦测试周期完全完成，然后测试关闭报告，并准备测试指标。</p><ul><li>进入条件 - 测试用例执行报告。缺陷报告</li><li>活动行为 - 它根据测试覆盖率，质量，时间消耗，成本和关键业务目标评估软件的完成标准。缺陷记录分析通过对类型和严重性进行分类来找出缺陷分布。</li><li>交付成果 - 关闭报告，测试指标</li></ul><h4 id="测试周期"><a href="#测试周期" class="headerlink" title="测试周期"></a>测试周期</h4><p>关闭测试周期结束报告包括与软件设计，开发，测试结果和缺陷报告相关的所有文档。如果存在具有相同规范的软件，此阶段将评估开发策略，测试过程，可能的缺陷，以便将来使用这些实践。</p><ul><li>进入条件 - 所有与软件相关的文档和报告。</li><li>活动行为 - 如果存在具有相同规范的软件，则评估开发策略，测试过程，将来可能存在的缺陷以使用这些实践。</li><li>交付成果 - 测试结束报告。</li></ul><h3 id="质量保证和软件质量控制"><a href="#质量保证和软件质量控制" class="headerlink" title="质量保证和软件质量控制"></a>质量保证和软件质量控制</h3><p>软件质量保证(也称为QA)是一系列任务，用于防止缺陷并确保为特定应用程序设计的技术，方法，方法和过程必须正确实施。这是软件系统开发过程中的持续过程。 应用程序单元的开发按照其开发顺序在质量保证规范下进行检查。 质量保证测试确保了高质量软件的开发，因为它主要关注软件开发过程中的高质量流程，良好的质量管理体系和定期的一致性审核。它是一种管理工具，包括计划和系统的活动和文件，以防止与质量有关的问题。</p><p>软件质量保证的责任不是任何特定的团队，而是开发团队的每个成员的责任。</p><ul><li>软件质量保证可防止缺陷。</li><li>软件质量保证是面向过程的。</li><li>软件质量保证在流程和预防性方面具有前瞻性。</li><li>软件质量保证是一种管理工具。</li><li>每个开发人员都负责软件质量保证。</li></ul><h4 id="软件质量控制"><a href="#软件质量控制" class="headerlink" title="软件质量控制"></a>软件质量控制</h4><p>软件质量控制也称为质量控制，是一系列任务，通过识别缺陷和纠正开发软件中的缺陷来确保软件质量。这是一个被动的过程，此过程的主要目的是在发布软件之前纠正所有类型的缺陷。通过纠正工具消除问题根源(导致质量低下)，从而使软件能够满足客户的要求和高质量，从而完成该过程。</p><p>质量控制的责任在于一个特定的团队，称为测试团队，通过验证和纠正工具测试软件的缺陷。</p><ul><li>质量控制提供缺陷识别。</li><li>质量控制是以产品为导向。</li><li>质量控制是一种纠正工具。</li><li>测试团队负责质量控制。</li><li>质量控制是一个反应过程。</li></ul><h4 id="质量保证与质量控制的区别"><a href="#质量保证与质量控制的区别" class="headerlink" title="质量保证与质量控制的区别"></a>质量保证与质量控制的区别</h4><p>软件质量保证与质量控制的区别如下表所示：<br>|项目|质量保证|质量控制|<br>|——|——|——|<br>|定义|质量保证是一组活动，可确保始终保持软件开发过程中使用的过程质量。|QC是一组用于检测已开发软件中的缺陷的活动。|<br>|关注重点|QA的重点是通过关注流程来防止开发软件中的缺陷。|QC的重点是通过关注测试过程来识别开发软件中的缺陷。|<br>|如何做|建立高质量的管理系统，并定期审核开发软件的操作是否符合要求。|通过使用开发软件中的测试技术和工具来检测和消除质量问题元素。|<br>|为什么做|质量保证通过使用包括文档在内的系统活动来确保质量问题的预防。|QC通过使用流程和技术来实现和维护高质量的软件，从而确保识别和消除缺陷。|<br>|面向|质量保证是面向流程的。|QC是面向产品的。|<br>|责任|开发团队的每个成员都负责QA|只有特定的测试团队负责QC|<br>|示例|验证软件流程|检验软件功能和流程|</p>]]></content>
<categories>
<category> 测试 </category>
</categories>
<tags>
<tag> 软件测试 </tag>
</tags>
</entry>
<entry>
<title>Spring 学习笔记</title>
<link href="/posts/4.html"/>
<url>/posts/4.html</url>
<content type="html"><![CDATA[<!-- markdownlint-disable MD025 --><h1 id="Spring开端"><a href="#Spring开端" class="headerlink" title="Spring开端"></a>Spring开端</h1><h2 id="Spring项目的创建"><a href="#Spring项目的创建" class="headerlink" title="Spring项目的创建"></a>Spring项目的创建</h2><p>首先，我们用Maven创建工程并引入<code>spring-context</code>依赖：</p><figure class="highlight xml"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag"><<span class="name">dependency</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">groupId</span>></span>org.springframework<span class="tag"></<span class="name">groupId</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">artifactId</span>></span>spring-context<span class="tag"></<span class="name">artifactId</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">version</span>></span>6.0.8<span class="tag"></<span class="name">version</span>></span></span><br><span class="line"><span class="tag"></<span class="name">dependency</span>></span></span><br><span class="line"><span class="tag"><<span class="name">dependency</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">groupId</span>></span>org.springframework<span class="tag"></<span class="name">groupId</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">artifactId</span>></span>spring-webmvc<span class="tag"></<span class="name">artifactId</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">version</span>></span>5.2.6.RELEASE<span class="tag"></<span class="name">version</span>></span></span><br><span class="line"><span class="tag"></<span class="name">dependency</span>></span></span><br></pre></td></tr></table></figure><p>我们先编写一个<code>MailService</code>，用于在用户登录和注册成功后发送邮件通知：</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">MailService</span> {</span><br><span class="line"> <span class="keyword">private</span> <span class="type">ZoneId</span> <span class="variable">zoneId</span> <span class="operator">=</span> ZoneId.systemDefault();</span><br><span class="line"></span><br><span class="line"> <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">setZoneId</span><span class="params">(ZoneId zoneId)</span> {</span><br><span class="line"> <span class="built_in">this</span>.zoneId = zoneId;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="keyword">public</span> String <span class="title function_">getTime</span><span class="params">()</span> {</span><br><span class="line"> <span class="keyword">return</span> ZonedDateTime.now(<span class="built_in">this</span>.zoneId).format(DateTimeFormatter.ISO_ZONED_DATE_TIME);</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">sendLoginMail</span><span class="params">(User user)</span> {</span><br><span class="line"> System.err.println(String.format(<span class="string">"Hi, %s! You are logged in at %s"</span>, user.getName(), getTime()));</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">sendRegistrationMail</span><span class="params">(User user)</span> {</span><br><span class="line"> System.err.println(String.format(<span class="string">"Welcome, %s!"</span>, user.getName()));</span><br><span class="line"></span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p>再编写一个<code>UserService</code>，实现用户注册和登录：</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">UserService</span> {</span><br><span class="line"> <span class="keyword">private</span> MailService mailService;</span><br><span class="line"></span><br><span class="line"> <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">setMailService</span><span class="params">(MailService mailService)</span> {</span><br><span class="line"> <span class="built_in">this</span>.mailService = mailService;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="keyword">private</span> List<User> users = <span class="keyword">new</span> <span class="title class_">ArrayList</span><>(List.of( <span class="comment">// users:</span></span><br><span class="line"> <span class="keyword">new</span> <span class="title class_">User</span>(<span class="number">1</span>, <span class="string">"[email protected]"</span>, <span class="string">"password"</span>, <span class="string">"Bob"</span>), <span class="comment">// bob</span></span><br><span class="line"> <span class="keyword">new</span> <span class="title class_">User</span>(<span class="number">2</span>, <span class="string">"[email protected]"</span>, <span class="string">"password"</span>, <span class="string">"Alice"</span>), <span class="comment">// alice</span></span><br><span class="line"> <span class="keyword">new</span> <span class="title class_">User</span>(<span class="number">3</span>, <span class="string">"[email protected]"</span>, <span class="string">"password"</span>, <span class="string">"Tom"</span>))); <span class="comment">// tom</span></span><br><span class="line"></span><br><span class="line"> <span class="keyword">public</span> User <span class="title function_">login</span><span class="params">(String email, String password)</span> {</span><br><span class="line"> <span class="keyword">for</span> (User user : users) {</span><br><span class="line"> <span class="keyword">if</span> (user.getEmail().equalsIgnoreCase(email) && user.getPassword().equals(password)) {</span><br><span class="line"> mailService.sendLoginMail(user);</span><br><span class="line"> <span class="keyword">return</span> user;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">RuntimeException</span>(<span class="string">"login failed."</span>);</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="keyword">public</span> User <span class="title function_">getUser</span><span class="params">(<span class="type">long</span> id)</span> {</span><br><span class="line"> <span class="keyword">return</span> <span class="built_in">this</span>.users.stream().filter(user -> user.getId() == id).findFirst().orElseThrow();</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="keyword">public</span> User <span class="title function_">register</span><span class="params">(String email, String password, String name)</span> {</span><br><span class="line"> users.forEach((user) -> {</span><br><span class="line"> <span class="keyword">if</span> (user.getEmail().equalsIgnoreCase(email)) {</span><br><span class="line"> <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">RuntimeException</span>(<span class="string">"email exist."</span>);</span><br><span class="line"> }</span><br><span class="line"> });</span><br><span class="line"> <span class="type">User</span> <span class="variable">user</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">User</span>(users.stream().mapToLong(u -> u.getId()).max().getAsLong() + <span class="number">1</span>, email, password, name);</span><br><span class="line"> users.add(user);</span><br><span class="line"> mailService.sendRegistrationMail(user);</span><br><span class="line"> <span class="keyword">return</span> user;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p>注意到<code>UserService</code>通过<code>setMailService()</code>注入了一个<code>MailService</code>。</p><p>然后，我们需要编写一个特定的<code>application.xml</code>配置文件，告诉Spring的IoC容器应该如何创建并组装Bean：</p><figure class="highlight xml"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta"><?xml version=<span class="string">"1.0"</span> encoding=<span class="string">"UTF-8"</span>?></span></span><br><span class="line"><span class="tag"><<span class="name">beans</span> <span class="attr">xmlns</span>=<span class="string">"http://www.springframework.org/schema/beans"</span></span></span><br><span class="line"><span class="tag"> <span class="attr">xmlns:xsi</span>=<span class="string">"http://www.w3.org/2001/XMLSchema-instance"</span></span></span><br><span class="line"><span class="tag"> <span class="attr">xsi:schemaLocation</span>=<span class="string">"http://www.springframework.org/schema/beans</span></span></span><br><span class="line"><span class="string"><span class="tag"> https://www.springframework.org/schema/beans/spring-beans.xsd"</span>></span></span><br><span class="line"></span><br><span class="line"> <span class="tag"><<span class="name">bean</span> <span class="attr">id</span>=<span class="string">"userService"</span> <span class="attr">class</span>=<span class="string">"com.itranswarp.learnjava.service.UserService"</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">property</span> <span class="attr">name</span>=<span class="string">"mailService"</span> <span class="attr">ref</span>=<span class="string">"mailService"</span> /></span></span><br><span class="line"> <span class="tag"></<span class="name">bean</span>></span></span><br><span class="line"></span><br><span class="line"> <span class="tag"><<span class="name">bean</span> <span class="attr">id</span>=<span class="string">"mailService"</span> <span class="attr">class</span>=<span class="string">"com.itranswarp.learnjava.service.MailService"</span> /></span></span><br><span class="line"><span class="tag"></<span class="name">beans</span>></span></span><br></pre></td></tr></table></figure><ul><li>每个<code><bean ...></code>都有一个<code>id</code>标识，相当于Bean的唯一ID；</li><li>在<code>userService</code>Bean中，通过<code><property name="..." ref="..." /></code>注入了另一个Bean；</li><li>Bean的顺序不重要，Spring根据依赖关系会自动正确初始化。</li></ul><p>把上述XML配置文件用Java代码写出来，就像这样：</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="type">UserService</span> <span class="variable">userService</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">UserService</span>();</span><br><span class="line"><span class="type">MailService</span> <span class="variable">mailService</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">MailService</span>();</span><br><span class="line">userService.setMailService(mailService);</span><br></pre></td></tr></table></figure><p>只不过Spring容器是通过读取XML文件后使用反射完成的。</p><p>如果注入的不是Bean，而是<code>boolean</code>、<code>int</code>、<code>String</code>这样的数据类型，则通过<code>value</code>注入，例如，创建一个<code>HikariDataSource</code>：</p><figure class="highlight xml"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag"><<span class="name">bean</span> <span class="attr">id</span>=<span class="string">"dataSource"</span> <span class="attr">class</span>=<span class="string">"com.zaxxer.hikari.HikariDataSource"</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">property</span> <span class="attr">name</span>=<span class="string">"jdbcUrl"</span> <span class="attr">value</span>=<span class="string">"jdbc:mysql://localhost:3306/test"</span> /></span></span><br><span class="line"> <span class="tag"><<span class="name">property</span> <span class="attr">name</span>=<span class="string">"username"</span> <span class="attr">value</span>=<span class="string">"root"</span> /></span></span><br><span class="line"> <span class="tag"><<span class="name">property</span> <span class="attr">name</span>=<span class="string">"password"</span> <span class="attr">value</span>=<span class="string">"password"</span> /></span></span><br><span class="line"> <span class="tag"><<span class="name">property</span> <span class="attr">name</span>=<span class="string">"maximumPoolSize"</span> <span class="attr">value</span>=<span class="string">"10"</span> /></span></span><br><span class="line"> <span class="tag"><<span class="name">property</span> <span class="attr">name</span>=<span class="string">"autoCommit"</span> <span class="attr">value</span>=<span class="string">"true"</span> /></span></span><br><span class="line"><span class="tag"></<span class="name">bean</span>></span></span><br></pre></td></tr></table></figure><p>最后一步，我们需要创建一个Spring的IoC容器实例，然后加载配置文件，让Spring容器为我们创建并装配好配置文件中指定的所有Bean，这只需要一行代码：</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">// 获取Bean:</span></span><br><span class="line"><span class="type">UserService</span> <span class="variable">userService</span> <span class="operator">=</span> context.getBean(UserService.class);</span><br><span class="line"><span class="comment">// 正常调用:</span></span><br><span class="line"><span class="type">User</span> <span class="variable">user</span> <span class="operator">=</span> userService.login(<span class="string">"[email protected]"</span>, <span class="string">"password"</span>);</span><br></pre></td></tr></table></figure><p>完整的<code>main()</code>方法如下：</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">Main</span> {</span><br><span class="line"> <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> {</span><br><span class="line"> <span class="type">ApplicationContext</span> <span class="variable">context</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">ClassPathXmlApplicationContext</span>(<span class="string">"application.xml"</span>);</span><br><span class="line"> <span class="type">UserService</span> <span class="variable">userService</span> <span class="operator">=</span> context.getBean(UserService.class);</span><br><span class="line"> <span class="type">User</span> <span class="variable">user</span> <span class="operator">=</span> userService.login(<span class="string">"[email protected]"</span>, <span class="string">"password"</span>);</span><br><span class="line"> System.out.println(user.getName());</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure><h3 id="ApplicationContext"><a href="#ApplicationContext" class="headerlink" title="ApplicationContext"></a>ApplicationContext</h3><p>我们从创建Spring容器的代码：</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"><span class="type">ApplicationContext</span> <span class="variable">context</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">ClassPathXmlApplicationContext</span>(<span class="string">"application.xml"</span>);</span><br></pre></td></tr></table></figure><p>可以看到，Spring容器就是<code>ApplicationContext</code>，它是一个接口，有很多实现类，这里我们选择<code>ClassPathXmlApplicationContext</code>，表示它会自动从classpath中查找指定的XML配置文件。</p><p>获得了<code>ApplicationContext</code>的实例，就获得了IoC容器的引用。从<code>ApplicationContext</code>中我们可以根据Bean的ID获取Bean，但更多的时候我们根据Bean的类型获取Bean的引用：</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"><span class="type">UserService</span> <span class="variable">userService</span> <span class="operator">=</span> context.getBean(UserService.class);</span><br></pre></td></tr></table></figure><p>Spring还提供另一种IoC容器叫<code>BeanFactory</code>，使用方式和<code>ApplicationContext</code>类似：</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="type">BeanFactory</span> <span class="variable">factory</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">XmlBeanFactory</span>(<span class="keyword">new</span> <span class="title class_">ClassPathResource</span>(<span class="string">"application.xml"</span>));</span><br><span class="line"><span class="type">MailService</span> <span class="variable">mailService</span> <span class="operator">=</span> factory.getBean(MailService.class);</span><br></pre></td></tr></table></figure><p><code>BeanFactory</code>和<code>ApplicationContext</code>的区别在于，<code>BeanFactory</code>的实现是按需创建，即第一次获取Bean时才创建这个Bean，而<code>ApplicationContext</code>会一次性创建所有的Bean。实际上，<code>ApplicationContext</code>接口是从<code>BeanFactory</code>接口继承而来的，并且，<code>ApplicationContext</code>提供了一些额外的功能，包括国际化支持、事件和通知机制等。通常情况下，我们总是使用<code>ApplicationContext</code>，很少会考虑使用<code>BeanFactory</code>。</p><h3 id="小结"><a href="#小结" class="headerlink" title="小结"></a>小结</h3><p>Spring的IoC容器接口是<code>ApplicationContext</code>，并提供了多种实现类；</p><p>通过XML配置文件创建IoC容器时，使用<code>ClassPathXmlApplicationContext</code>；</p><p>持有IoC容器后，通过<code>getBean()</code>方法获取Bean的引用。</p><h1 id="关于原型对象"><a href="#关于原型对象" class="headerlink" title="关于原型对象"></a>关于原型对象</h1><p>Spring默认使用单例模式（单例模式，整个生命周期都只有这一个对象，对象的唯一。），但是如果我们要让一个对象每次被实例化时产生的都是一个新对象，那我们就需要设置Bean的scope=”prototype”</p><h1 id="Spring自动装配"><a href="#Spring自动装配" class="headerlink" title="Spring自动装配"></a>Spring自动装配</h1><p>属性名：AutoWire 属性值：【ByName，ByType，constructor，default，no】</p><p>ByName：自动在容器上下文中寻找，和自己对象Set方法后面的值对应的BeanID，需要保证所有Bean的ID唯一性，并且这个Bean需要和自动注入的Set方法的值一致!</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><bean id=<span class="string">"people"</span> class=<span class="string">"People"</span> autowire=<span class="string">"byName"</span>></span><br><span class="line"> <property name=<span class="string">"name"</span> value=<span class="string">"王某"</span>/></span><br><span class="line"> </bean></span><br></pre></td></tr></table></figure><p>ByType：自动在容器上下文中寻找，和自己对象属性类型值相同的Bean，这时，我们可以取消ID属性，因为装配过程不再依赖于ID。需要保证所有Bean的Class唯一性，并且这个Bean需要和自动注入的属性的类型一致!</p><h1 id="使用注解实现自动装配"><a href="#使用注解实现自动装配" class="headerlink" title="使用注解实现自动装配"></a>使用注解实现自动装配</h1><h2 id="关于注解"><a href="#关于注解" class="headerlink" title="关于注解"></a>关于注解</h2><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Autowired</span>：根据属性类型进行自动装配，若接口不止一个实现，则按照属性名(因为可以不加set)进行匹配bean</span><br><span class="line"><span class="meta">@Qualifier</span>：必须配合Autowired使用，可以帮助指定实现类id</span><br><span class="line"><span class="meta">@Resource</span>：可以根据类型注入，可以根据名称注入</span><br><span class="line"><span class="meta">@Value</span>：注入普通类型属性</span><br><span class="line"><span class="meta">@Autowired</span>：可以根据类型注入,可以根据名称注入（默认优先进行byType装配）</span><br><span class="line">若接口不止一个实现，则按照属性名(因为可以不加set)进行匹配bean</span><br><span class="line">创建实体类对象，在实体类中对象类型属性上或set方法上加上该注解。</span><br><span class="line">加入该注解后，该属性可以不需要添加set方法</span><br><span class="line"><span class="meta">@Qualifier</span>：若Autowired按属性名匹配，则可以配合<span class="meta">@Qualifier</span> 注解指定实现类id</span><br><span class="line"><span class="meta">@Resource</span>: 可以根据类型注入，可以根据名称注入（默认优先进行byName装配）</span><br><span class="line">如果同时指定了name和type，则从Spring上下文中找到唯一匹配的bean进行装配，找不到则抛出异常</span><br><span class="line">如果指定了name，则从上下文中查找名称（id）匹配的bean进行装配，找不到则抛出异常</span><br><span class="line">如果指定了type，则从上下文中找到类型匹配的唯一bean进行装配，找不到或者找到多个，都会抛出异常</span><br><span class="line">如果既没有指定name，又没有指定type，则自动按照byName方式进行装配；如果没有匹配，则回退为一个原始类型进行匹配，如果匹配则自动装配；</span><br><span class="line"><span class="meta">@Value</span>：注入普通类型属性</span><br><span class="line">代替了<property name=<span class="string">"..."</span> value=<span class="string">"..."</span>/> 的繁琐操作。</span><br></pre></td></tr></table></figure><p>使用注解须知：</p><p>1.导入约束 context约束<br><!-- markdownlint-disable MD036 --><br><strong>2.配置注解的支持 context:annotation-config</strong></p><figure class="highlight xml"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta"><?xml version=<span class="string">"1.0"</span> encoding=<span class="string">"UTF-8"</span>?></span></span><br><span class="line"><span class="tag"><<span class="name">beans</span> <span class="attr">xmlns</span>=<span class="string">"http://www.springframework.org/schema/beans"</span></span></span><br><span class="line"><span class="tag"> <span class="attr">xmlns:xsi</span>=<span class="string">"http://www.w3.org/2001/XMLSchema-instance"</span></span></span><br><span class="line"><span class="tag"> <span class="attr">xmlns:context</span>=<span class="string">"http://www.springframework.org/schema/context"</span></span></span><br><span class="line"><span class="tag"> <span class="attr">xsi:schemaLocation</span>=<span class="string">"http://www.springframework.org/schema/beans</span></span></span><br><span class="line"><span class="string"><span class="tag"> https://www.springframework.org/schema/beans/spring-beans.xsd</span></span></span><br><span class="line"><span class="string"><span class="tag"> http://www.springframework.org/schema/context</span></span></span><br><span class="line"><span class="string"><span class="tag"> https://www.springframework.org/schema/context/spring-context.xsd"</span>></span></span><br><span class="line"> <span class="tag"><<span class="name">context:annotation-config</span>/></span></span><br><span class="line"></span><br><span class="line"><span class="tag"></<span class="name">beans</span>></span></span><br></pre></td></tr></table></figure><p>@Autowired</p><p>直接在属性上使用即可!也可以在set上使用！</p><p>使用Autowired我们可以不用再编写set方法，前提是这个自动装配的属性在IOC（spring）容器中存在，且符合名字ByName！</p><p>科普：</p><figure class="highlight xml"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">@Nullable 字段标记了这个注解，说明这个字段可以为null；</span><br></pre></td></tr></table></figure><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line"><span class="literal">false</span>值可以为<span class="literal">null</span></span><br><span class="line"><span class="meta">@Autowired(required = false)</span></span><br><span class="line">另外还有<span class="meta">@Resource</span>注解（自动通过名字，类型，注入）</span><br><span class="line"><span class="meta">@Component</span>（组件，放在类上，说明这个类被Spring管理；了，这就是Bean）</span><br><span class="line"></span><br></pre></td></tr></table></figure><h2 id="Component衍生注解"><a href="#Component衍生注解" class="headerlink" title="@Component衍生注解"></a>@Component衍生注解</h2><p>@Component拥有几个衍生注解，在之后的SpringMVC中会进行三层架构分层</p><p>dao（@Repository）</p><p>Service（@Service）</p><p>controller（@Controller）</p><p>四个注解功能是一样的，都是将某个类注册到Spring中，装配Bean</p><h3 id="自动装配"><a href="#自动装配" class="headerlink" title="自动装配"></a>自动装配</h3><figure class="highlight text"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">@Autowired不能唯一自动装配注解：自动装配通过类型，名字</span><br><span class="line">如果@Autowired不能唯一自动装配注解，那么就需要@Qualifier(value="")</span><br><span class="line"></span><br></pre></td></tr></table></figure><h3 id="作用域"><a href="#作用域" class="headerlink" title="作用域"></a>作用域</h3><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Component</span></span><br><span class="line"><span class="meta">@Scope("prototype")</span></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">User</span> {</span><br><span class="line"> <span class="meta">@Value("小王")</span></span><br><span class="line"> <span class="keyword">public</span> String name;</span><br><span class="line"></span><br><span class="line">}</span><br></pre></td></tr></table></figure><h1 id="完全使用Java方式配置Spring"><a href="#完全使用Java方式配置Spring" class="headerlink" title="完全使用Java方式配置Spring"></a>完全使用Java方式配置Spring</h1><p>配置文件：</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> top.yuanfangwa.Config;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> org.springframework.context.annotation.Bean;</span><br><span class="line"><span class="keyword">import</span> org.springframework.context.annotation.ComponentScan;</span><br><span class="line"><span class="keyword">import</span> org.springframework.context.annotation.Configuration;</span><br><span class="line"><span class="keyword">import</span> top.yuanfangwa.pojo.USer;</span><br><span class="line"></span><br><span class="line"><span class="comment">/**</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@Author</span>：无知啊</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@ProJect</span>_Name：SpringDemo</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@Date</span>：2022/3/1214:20</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@Description</span>:</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@Since</span> version:1.0</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="comment">//这个也会被Spring容器接管，因为他本身也是一个Component，</span></span><br><span class="line"><span class="comment">// @Configuration代表着这是一个配置类，就和之前的Beans.xml是一样的</span></span><br><span class="line"><span class="meta">@Configuration</span></span><br><span class="line"><span class="meta">@ComponentScan("top.yuanfangwa.pojo")</span></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">Config</span> {</span><br><span class="line"><span class="comment">//注册一个Bean就相当于我们之前写的一个Bean标签</span></span><br><span class="line"><span class="comment">//方法名就相当于之前Bean标签的ID属性</span></span><br><span class="line"><span class="comment">// 返回值就相当于之前的class属性</span></span><br><span class="line"> <span class="meta">@Bean</span></span><br><span class="line"> <span class="keyword">public</span> USer <span class="title function_">getBean</span><span class="params">()</span> {</span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">new</span> <span class="title class_">USer</span>();<span class="comment">//就是要返回的Bean</span></span><br><span class="line"> }</span><br><span class="line">}</span><br><span class="line"></span><br></pre></td></tr></table></figure><p>测试：</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">import</span> org.springframework.context.ApplicationContext;</span><br><span class="line"><span class="keyword">import</span> org.springframework.context.annotation.AnnotationConfigApplicationContext;</span><br><span class="line"><span class="keyword">import</span> top.yuanfangwa.Config.Config;</span><br><span class="line"><span class="keyword">import</span> top.yuanfangwa.pojo.USer;</span><br><span class="line"></span><br><span class="line"><span class="comment">/**</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@Author</span>：无知啊</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@ProJect</span>_Name：SpringDemo</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@Date</span>：2022/3/1214:22</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@Description</span>:</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@Since</span> version:1.0</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">Mytset</span> {</span><br><span class="line"> <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> {</span><br><span class="line"> <span class="type">ApplicationContext</span> <span class="variable">Context</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">AnnotationConfigApplicationContext</span>(Config.class);</span><br><span class="line"> <span class="type">USer</span> <span class="variable">user</span> <span class="operator">=</span> (USer) Context.getBean(<span class="string">"getBean"</span>);</span><br><span class="line"> System.out.println(user.getName());</span><br><span class="line"></span><br><span class="line"> }</span><br><span class="line">}</span><br><span class="line"></span><br></pre></td></tr></table></figure><p>这样的配置在Spring boot中随处可见</p><h1 id="代理模式"><a href="#代理模式" class="headerlink" title="代理模式"></a>代理模式</h1><p>代理模式可以使得原本的操作变得纯粹</p><h1 id="aop约束"><a href="#aop约束" class="headerlink" title="aop约束"></a>aop约束</h1><figure class="highlight xml"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta"><?xml version=<span class="string">"1.0"</span> encoding=<span class="string">"UTF-8"</span>?></span></span><br><span class="line"><span class="tag"><<span class="name">beans</span> <span class="attr">xmlns</span>=<span class="string">"http://www.springframework.org/schema/beans"</span></span></span><br><span class="line"><span class="tag"> <span class="attr">xmlns:xsi</span>=<span class="string">"http://www.w3.org/2001/XMLSchema-instance"</span></span></span><br><span class="line"><span class="tag"> <span class="attr">xmlns:aop</span>=<span class="string">"http://www.springframework.org/schema/aop"</span></span></span><br><span class="line"><span class="tag"> <span class="attr">xsi:schemaLocation</span>=<span class="string">"http://www.springframework.org/schema/beans</span></span></span><br><span class="line"><span class="string"><span class="tag"> https://www.springframework.org/schema/beans/spring-beans.xsd</span></span></span><br><span class="line"><span class="string"><span class="tag"> http://www.springframework.org/schema/aop</span></span></span><br><span class="line"><span class="string"><span class="tag"> https://www.springframework.org/schema/aop/spring-aop.xsd"</span>></span></span><br><span class="line"><span class="tag"></<span class="name">beans</span>></span></span><br></pre></td></tr></table></figure><h1 id="Aop-表达式"><a href="#Aop-表达式" class="headerlink" title="Aop 表达式"></a>Aop 表达式</h1><p>Aop中expression表达式的表示方法</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br></pre></td><td class="code"><pre><span class="line">常见的切面表达式</span><br><span class="line"><span class="number">1</span> 所有公有方法的执行</span><br><span class="line"></span><br><span class="line">execution(<span class="keyword">public</span> * *(..))</span><br><span class="line"></span><br><span class="line"><span class="number">2</span> 所有以set开头的公有方法的执行</span><br><span class="line"></span><br><span class="line">execution(* set*(..))</span><br><span class="line"></span><br><span class="line"><span class="number">3</span> AccountService接口下的所有方法的执行</span><br><span class="line"></span><br><span class="line">execution(* com.LightseaBlue.service.AccountService.*(..))</span><br><span class="line"></span><br><span class="line"><span class="number">4</span> com.LightseaBlue.service包下的所有方法的执行</span><br><span class="line"></span><br><span class="line">execution(* com.LightseaBlue.service.*.*(..))</span><br><span class="line"></span><br><span class="line"><span class="number">5</span> com.LightseaBlue.service包及其子包下的所有方法的执行</span><br><span class="line"></span><br><span class="line">execution(* com.LightseaBlue.service..*.*(..))</span><br><span class="line"></span><br><span class="line"><span class="number">6</span> 匹配com.LightseaBlue.service包下的所有类的所有方法（不含子包）</span><br><span class="line"></span><br><span class="line">within(com.LightseaBlue.service.*)</span><br><span class="line"></span><br><span class="line"><span class="number">7</span> com.LightseaBlue.service包和子包的所有方法</span><br><span class="line"></span><br><span class="line">within(com.LightseaBlue.service..*)</span><br><span class="line"></span><br><span class="line"><span class="number">8</span> 匹配AccountService的代理类（不支持通配符）</span><br><span class="line"></span><br><span class="line"><span class="built_in">this</span>(com.LightseaBlue.service.AccountService)</span><br></pre></td></tr></table></figure><h1 id="spring整合Mybatis"><a href="#spring整合Mybatis" class="headerlink" title="spring整合Mybatis"></a>spring整合Mybatis</h1><!-- markdownlint-disable MD001 --><h3 id="约束"><a href="#约束" class="headerlink" title="约束"></a>约束</h3><figure class="highlight xml"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line"><span class="tag"><<span class="name">beans</span> <span class="attr">xmlns</span>=<span class="string">"http://www.springframework.org/schema/beans"</span></span></span><br><span class="line"><span class="tag"> <span class="attr">xmlns:xsi</span>=<span class="string">"http://www.w3.org/2001/XMLSchema-instance"</span></span></span><br><span class="line"><span class="tag"> <span class="attr">xmlns:aop</span>=<span class="string">"http://www.springframework.org/schema/aop"</span></span></span><br><span class="line"><span class="tag"> <span class="attr">xmlns:tx</span>=<span class="string">"http://www.springframework.org/schema/tx"</span></span></span><br><span class="line"><span class="tag"> <span class="attr">xsi:schemaLocation</span>=<span class="string">"http://www.springframework.org/schema/beans</span></span></span><br><span class="line"><span class="string"><span class="tag">https://www.springframework.org/schema/beans/spring-beans.xsd</span></span></span><br><span class="line"><span class="string"><span class="tag">http://www.springframework.org/schema/aop</span></span></span><br><span class="line"><span class="string"><span class="tag">https://www.springframework.org/schema/aop/spring-aop.xsd</span></span></span><br><span class="line"><span class="string"><span class="tag"> http://www.springframework.org/schema/tx</span></span></span><br><span class="line"><span class="string"><span class="tag"> https://www.springframework.org/schema/aop/spring-tx.xsd"</span>></span></span><br><span class="line"><span class="tag"></<span class="name">beans</span>></span></span><br></pre></td></tr></table></figure><p>总体来说，Spring负责了我们原本所需要负责的所有事情，我们只需要去设定实体类以及注入所需要的信息。</p><h1 id="spring-事务"><a href="#spring-事务" class="headerlink" title="spring 事务"></a>spring 事务</h1><p>默认情况下只会回滚<code>RuntimeException</code>（运行时异常）和<code>Error</code>（错误），对于普通的 Exception（非运行时异常），它不会回滚。回滚生效也是有范围的，需处于public</p>]]></content>
<categories>
<category> 编程 </category>
<category> Java </category>
</categories>
<tags>
<tag> Spring </tag>
</tags>
</entry>
<entry>
<title>Java基础！</title>
<link href="/posts/2.html"/>
<url>/posts/2.html</url>
<content type="html"><![CDATA[<h2 id="一、修饰符"><a href="#一、修饰符" class="headerlink" title="一、修饰符"></a>一、修饰符</h2><h3 id="1、final"><a href="#1、final" class="headerlink" title="1、final"></a>1、<strong>final</strong></h3><h4 id="final关键字是最终的意思，可以修饰成员方法，成员变量，类"><a href="#final关键字是最终的意思，可以修饰成员方法，成员变量，类" class="headerlink" title="final关键字是最终的意思，可以修饰成员方法，成员变量，类"></a>final关键字是最终的意思，可以修饰成员方法，成员变量，类</h4><p><strong>final</strong>修饰的特点：</p><ul><li>修饰方法：表面该方法是最终的方法，<strong><em>不能被重写</em></strong></li><li>修饰变量：表明该变量是常量，<strong><em>不能再次被赋值</em></strong></li><li>修饰类：表明该类是最终类，<strong><em>不能被继承</em></strong></li></ul><h4 id="final修饰局部变量"><a href="#final修饰局部变量" class="headerlink" title="final修饰局部变量"></a><strong>final</strong>修饰局部变量</h4><ul><li>变量是基本数据类型：final修饰指的是基本数据类型的<strong><em>数据值</em></strong>不能发生改变</li><li>变量是引用数据类型：final修饰指的是音乐数据类型的<strong><em>地址值</em></strong>不能发生改变，但是地址值里面的内容是可以发生改变的</li></ul><h4 id="2、static"><a href="#2、static" class="headerlink" title="2、static"></a>2、static</h4><h4 id="static关键字是静态的意思，可以修饰成员方法，成员变量"><a href="#static关键字是静态的意思，可以修饰成员方法，成员变量" class="headerlink" title="static关键字是静态的意思，可以修饰成员方法，成员变量"></a><strong><em>static</em></strong>关键字是静态的意思，可以修饰成员方法，成员变量</h4><p><strong><em>static</em></strong>修饰的特点：</p><ul><li>该类的所有对象共享</li></ul><p>这也是判断是否使用静态关键字的条件</p><ul><li>可以通过类名调用</li></ul><p>也可以通过对象名调用</p><p><strong><em>static</em></strong>访问特点：</p><p>非静态的成员方法：（没有被static修饰符修饰过的成员方法）</p><ul><li>能访问静态的成员变量</li><li>能访问非静态的成员变量</li><li>能访问静态的成员方法</li><li>能访问非静态的成员方法</li></ul><p>静态的成员方法（被static修饰符修饰过的成员方法）</p><ul><li>能访问静态的成员变量</li><li>能访问静态的成员方法</li></ul><p><strong>总结：静态成员方法只能访问静态成员</strong></p><h1 id="二、多态"><a href="#二、多态" class="headerlink" title="二、多态"></a>二、多态</h1><h2 id="1-1-多态概述"><a href="#1-1-多态概述" class="headerlink" title="1.1 多态概述"></a>1.1 多态概述</h2><p>同一个对象，在不同时刻表现出来的不同形态</p><p>例：猫</p><p>可以说猫是猫：<strong>猫 cat = new 猫（）；</strong></p><p>也可以说猫是动物：<strong>动物 animal = new 猫（）；</strong></p><p>这里猫在不同时刻表现出来了不同的形态，这就是多态</p><p>多态的前提和体现</p><ul><li><p>有继承/实现关系</p></li><li><p>有方法重写</p></li><li><p>有父类引用指向子类</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"><span class="type">Animal</span> <span class="variable">animal</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Cat</span>(); <span class="comment">//这就是父类引用指向子类</span></span><br></pre></td></tr></table></figure></li></ul><h3 id="1-2-多态中成员访问特点"><a href="#1-2-多态中成员访问特点" class="headerlink" title="1.2 多态中成员访问特点"></a>1.2 多态中成员访问特点</h3><ul><li><strong>成员变量：</strong>编译看左边，运行看左边</li><li><strong>成员方法：</strong>编译看左边，运行看右边</li></ul><p>为什么成员变量和成员方法的访问不一样？</p><ul><li>因为成员方法有重写，而成员变量没有</li></ul><h4 id="1-3-多态的好处和弊端"><a href="#1-3-多态的好处和弊端" class="headerlink" title="1.3 多态的好处和弊端"></a>1.3 多态的好处和弊端</h4><ul><li>多态的好处：提高程序的拓展性</li></ul><p>具体体现：定义方法的时候，使用父类型作为参数，将来在使用的时候，使用具体的子类型参与操作</p><ul><li>多态的弊端：不能使用子类的特有功能（不能使用子类的成员方法）</li></ul><h4 id="1-4-多态中的转型"><a href="#1-4-多态中的转型" class="headerlink" title="1.4 多态中的转型"></a>1.4 多态中的转型</h4><ul><li>向上转型</li></ul><p>从子到父</p><p>父类引用指向子类对象</p><ul><li>向下转型</li></ul><p>从父到子</p><p>父类引用转为子类对象</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">AnimalDemo</span> {</span><br><span class="line"> <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> {</span><br><span class="line"> <span class="comment">//多态</span></span><br><span class="line"> <span class="type">Animal</span> <span class="variable">a</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Cat</span>(); <span class="comment">// 向上转型</span></span><br><span class="line"> a.eat();</span><br><span class="line"></span><br><span class="line"> <span class="comment">// 向下转型</span></span><br><span class="line"> <span class="type">Cat</span> <span class="variable">c</span> <span class="operator">=</span> (Cat)a;</span><br><span class="line"> c.eat();</span><br><span class="line"> c.playGame();</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure><h1 id="三、抽象类"><a href="#三、抽象类" class="headerlink" title="三、抽象类"></a>三、抽象类</h1><h2 id="1-1-抽象类概述"><a href="#1-1-抽象类概述" class="headerlink" title="1.1 抽象类概述"></a>1.1 抽象类概述</h2><p> 在Java中，一个<strong>没用方法体</strong>的方法应该定义为<strong>抽象方法</strong>，而类中如果有<strong>抽象方法</strong>，则该类必须定义为<strong>抽象类</strong></p><h2 id="1-2-抽象类的特点"><a href="#1-2-抽象类的特点" class="headerlink" title="1.2 抽象类的特点"></a>1.2 抽象类的特点</h2><ul><li><p>抽象类和抽象方法必须用<strong>abstract</strong>关键字修饰</p><p> public <strong>abstract</strong>class 类名{}</p><p> public <strong>abstract</strong>void eat();</p></li><li><p>抽象类中不一定有抽象方法，有抽象方法的类一定是抽象类</p></li><li><p>抽象类不能实例化</p></li></ul><p> 可以参照抽象的方式，通过子类对象实例化，这叫抽象类多态</p><ul><li>抽象类的子类</li></ul><p> 要么重写抽象类中的所有抽象方法</p><p> 要么是抽象类（把子类也定义成抽象类）</p><h2 id="1-3-抽象类的成员特点"><a href="#1-3-抽象类的成员特点" class="headerlink" title="1.3 抽象类的成员特点"></a>1.3 抽象类的成员特点</h2><ul><li>成员变量</li></ul><p> 可以是变量</p><p> 也可以是常量</p><ul><li>构造方法</li></ul><p> 有构造方法，但是不能实例化</p><p> 构造方法的作用？ 用于子类访问父类数据的初始化</p><ul><li>成员方法</li></ul><p> 可以有抽象方法：限定子类必须完成某些动作</p><p> 也可以有非抽象方法：提高代码复用性</p><h1 id="四、接口"><a href="#四、接口" class="headerlink" title="四、接口"></a>四、接口</h1><h2 id="1-1-接口概述"><a href="#1-1-接口概述" class="headerlink" title="1.1 接口概述"></a>1.1 接口概述</h2><p> 接口就是一种<strong>公共的规范标准</strong>，只要符合规范标准，都可以通用Java中的接口，更多的体现在<strong>对行为的抽象</strong></p><h2 id="1-2-接口的特点"><a href="#1-2-接口的特点" class="headerlink" title="1.2 接口的特点"></a>1.2 接口的特点</h2><ul><li>接口用关键字interface修饰</li></ul><p> public <strong>interface</strong> 接口名{}</p><ul><li>类实现接口用implements表示</li></ul><p> public class 类名 implements 接口名 {}</p><ul><li>接口不能实例化</li></ul><p> 接口实例化按照多态的方式，通过实现类对象实例化，这叫接口多态</p><p> 多态的形式：具体类多态，<strong>抽象类多态，接口多态</strong></p><p> 多态的前提：有继承或者实现关系；有方法重写；有父（类/接口）引用指向（子/实现）类对象</p><ul><li>接口的实现类</li></ul><p> 要么重写接口中的所有抽象方法</p><p> 要么是抽象类</p><h2 id="1-3-接口的成员特点"><a href="#1-3-接口的成员特点" class="headerlink" title="1.3 接口的成员特点"></a>1.3 接口的成员特点</h2><ul><li>成员变量</li></ul><p> 只能是常量</p><p> 默认修饰符：<strong>public static final</strong></p><ul><li>构造方法</li></ul><p> 接口没用构造方法，因为接口主要是对行为进行抽象的，没用具体存在</p><p> 一个类如果没用父类，默认继承Object类</p><ul><li>成员方法</li></ul><p> 只能是抽象方法</p><p> 默认修饰符：public abstract</p><h2 id="1-4-类和接口的关系"><a href="#1-4-类和接口的关系" class="headerlink" title="1.4 类和接口的关系"></a>1.4 类和接口的关系</h2><ul><li>类和类的关系</li></ul><p> 继承关系，只能单继承，但是可以多层继承</p><ul><li>类和接口的关系</li></ul><p> 实现关系，可以单实现，也可以多实现，还可以在继承一个类的同时实现多个接口</p><ul><li>接口和接口的关系</li></ul><p> 继承关系，可以单继承，也可以多继承</p><h2 id="1-5-抽象类和接口的区别"><a href="#1-5-抽象类和接口的区别" class="headerlink" title="1.5 抽象类和接口的区别"></a>1.5 抽象类和接口的区别</h2><ul><li>成员区别</li></ul><p> 抽象类 变量，常量；有构造方法；由抽象方法；也有非抽象方法</p><p> 接口 常量，抽象方法</p><ul><li>关系区别</li></ul><p> 类与类 继承，单继承</p><p> 类与接口 实现，可以单实现，也可以多实现</p><p> 接口与接口 继承，单实现，多继承</p><ul><li>设计理念区别</li></ul><p> 抽象类 对类抽象，包括属性、行为</p><p> 接口 对行为抽象，主要是行为</p><h1 id="五、内部类"><a href="#五、内部类" class="headerlink" title="五、内部类"></a>五、内部类</h1><h2 id="1-1-内部类概述"><a href="#1-1-内部类概述" class="headerlink" title="1.1 内部类概述"></a>1.1 内部类概述</h2><p> 内部类：就是在一个类中定义一个类。 例：在一个类A的内部定义一个类B，类B就是内部类</p><p> 内部类定义格式</p><ul><li>格式</li></ul><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> class 类名 {</span><br><span class="line"> 修饰符 class 类名 {</span><br><span class="line"></span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure><ul><li>范例</li></ul><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">Outer</span> {</span><br><span class="line"> <span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">Inner</span> {</span><br><span class="line"></span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure><blockquote><p>内部类访问特点</p></blockquote><ul><li>内部类可以直接访问外部类的成员，包括私有</li><li>外部类要访问内部类的成员，必须创建对象</li></ul><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">Outer</span> {</span><br><span class="line"> <span class="comment">// 创建内部类</span></span><br><span class="line"> <span class="keyword">private</span> <span class="keyword">class</span> <span class="title class_">Inner</span> {</span><br><span class="line"> <span class="keyword">void</span> <span class="title function_">show</span><span class="params">()</span> {</span><br><span class="line"> System.out.println(age);</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="comment">// method()这个方法存在的意义就是调用Inner这个内部类的show()方法</span></span><br><span class="line"> <span class="keyword">void</span> <span class="title function_">method</span><span class="params">()</span> {</span><br><span class="line"> <span class="comment">// 在method()方法里创建内部类对象，并调用</span></span><br><span class="line"> <span class="type">Inner</span> <span class="variable">in</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Inner</span>();</span><br><span class="line"> in.show();</span><br><span class="line"> }</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"></span><br><span class="line"><span class="comment">// 内部类测试类</span></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">Demo</span> {</span><br><span class="line"> <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> {</span><br><span class="line"> <span class="comment">// 创建Outer类对象</span></span><br><span class="line"> <span class="type">Outer</span> <span class="variable">o</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Outer</span>();</span><br><span class="line"> <span class="comment">// 调用 method() 方法就相当于调用了内部类里面的 show() 方法</span></span><br><span class="line"> o.method();</span><br><span class="line"> }</span><br><span class="line">}</span><br><span class="line">}</span><br></pre></td></tr></table></figure><h2 id="1-2-局部内部类"><a href="#1-2-局部内部类" class="headerlink" title="1.2 局部内部类"></a>1.2 局部内部类</h2><blockquote><p>局部内部类特点：</p></blockquote><p> 局部内部类是在方法中定义类，所以外界是无法直接使用的，需要在方法内部创建对象并使用。</p><p> 该类可以直接访问外部的成员，也可以访问方法内的局部变量。</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">Outer</span> {</span><br><span class="line"> <span class="keyword">private</span> <span class="type">int</span> <span class="variable">num</span> <span class="operator">=</span> <span class="number">10</span>;</span><br><span class="line"></span><br><span class="line"> <span class="keyword">void</span> <span class="title function_">method</span><span class="params">()</span> {</span><br><span class="line"> <span class="type">int</span> <span class="variable">num2</span> <span class="operator">=</span> <span class="number">20</span>;</span><br><span class="line"> <span class="keyword">class</span> <span class="title class_">Inner</span> {</span><br><span class="line"> <span class="keyword">void</span> <span class="title function_">show</span><span class="params">()</span> {</span><br><span class="line"> System.out.println(num);</span><br><span class="line"> System.out.println(num2);</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="type">Inner</span> <span class="variable">i</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Inner</span>();</span><br><span class="line"> i.show();</span><br><span class="line"> }</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">OuterDemo</span> {</span><br><span class="line"> <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> {</span><br><span class="line"> <span class="type">Outer</span> <span class="variable">o</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Outer</span>();</span><br><span class="line"> o.method();</span><br><span class="line"> }</span><br><span class="line">}</span><br><span class="line"></span><br></pre></td></tr></table></figure><h2 id="1-3-匿名内部类"><a href="#1-3-匿名内部类" class="headerlink" title="1.3 匿名内部类"></a>1.3 匿名内部类</h2><p> 前提：存在一个类或者接口，这里的类可以是具体类也可以是抽象类</p><ul><li>格式</li></ul><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">new</span> 类名或者接口名() {</span><br><span class="line"> 重写方法;</span><br><span class="line">}</span><br></pre></td></tr></table></figure><ul><li>范例</li></ul><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">new</span> <span class="title class_">Inter</span>() {</span><br><span class="line"> <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">show</span><span class="params">()</span> {</span><br><span class="line"></span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure><p><strong>匿名内部类本质：是一个继承了该类或者实现了该接口的子类匿名对象</strong></p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">interface</span> <span class="title class_">Inter</span> { <span class="comment">// 这是一个接口，里面有一个show()方法</span></span><br><span class="line"> <span class="keyword">void</span> <span class="title function_">show</span><span class="params">()</span>;</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">Outer</span> {</span><br><span class="line"> <span class="keyword">void</span> <span class="title function_">method</span><span class="params">()</span> {</span><br><span class="line"></span><br><span class="line"> <span class="keyword">new</span> <span class="title class_">Inter</span>() { <span class="comment">// n</span></span><br><span class="line"></span><br><span class="line"> <span class="meta">@Override</span></span><br><span class="line"> <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">show</span><span class="params">()</span> {</span><br><span class="line"> System.out.println(<span class="string">"匿名内部类"</span>);</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> }.show();</span><br><span class="line"></span><br><span class="line"> }</span><br><span class="line">}</span><br><span class="line"></span><br><span class="line"></span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">OuterDemo</span> {</span><br><span class="line"> <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> {</span><br><span class="line"> <span class="type">Outer</span> <span class="variable">o</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Outer</span>();</span><br><span class="line"> o.method();</span><br><span class="line"> }</span><br><span class="line">}</span><br><span class="line"></span><br></pre></td></tr></table></figure><h1 id="六、IO"><a href="#六、IO" class="headerlink" title="六、IO"></a>六、IO</h1><h2 id="字符缓冲流复制文件"><a href="#字符缓冲流复制文件" class="headerlink" title="字符缓冲流复制文件"></a>字符缓冲流复制文件</h2><ul><li><p>BufferedReder 字符缓冲输入流</p></li><li><p>BufferedWrite 字符缓冲输出流</p></li></ul><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.itheima.myIo.myCharStream.demo04;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> java.io.*;</span><br><span class="line"></span><br><span class="line"><span class="comment">/*</span></span><br><span class="line"><span class="comment"> 需求：</span></span><br><span class="line"><span class="comment"> 使用字符缓冲流特有功能复制Java文件</span></span><br><span class="line"><span class="comment"> 数据源：D:\IdeaProject\study\src\com\itheima\myIo\myOutputStream\FileOutputStreamDemo02.java</span></span><br><span class="line"><span class="comment"> 目的地：D:\IdeaProject\study\src\com\itheima\myIo\myCharStream\demo04\Copy.java</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">BufferStreamDemo04</span> {</span><br><span class="line"> <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> IOException {</span><br><span class="line"> <span class="comment">// 字符缓冲输入流</span></span><br><span class="line"> <span class="type">BufferedReader</span> <span class="variable">br</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">BufferedReader</span>(<span class="keyword">new</span> <span class="title class_">FileReader</span>(<span class="string">"D:\\IdeaProject\\study\\src\\com\\itheima\\myIo\\myOutputStream\\FileOutputStreamDemo02.java"</span>));</span><br><span class="line"> <span class="comment">// 字符缓冲输出流</span></span><br><span class="line"> <span class="type">BufferedWriter</span> <span class="variable">bw</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">BufferedWriter</span>(<span class="keyword">new</span> <span class="title class_">FileWriter</span>(<span class="string">"D:\\IdeaProject\\study\\src\\com\\itheima\\myIo\\myCharStream\\demo04\\Copy.java"</span>));</span><br><span class="line"></span><br><span class="line"> String line;</span><br><span class="line"> <span class="keyword">while</span> ((line = br.readLine()) != <span class="literal">null</span>) {</span><br><span class="line"> System.out.println(line);</span><br><span class="line"> bw.write(line);</span><br><span class="line"> bw.newLine();</span><br><span class="line"> bw.flush();</span><br><span class="line"> }</span><br><span class="line"> bw.close();</span><br><span class="line"> br.close();</span><br><span class="line"> }</span><br><span class="line">}</span><br><span class="line"></span><br></pre></td></tr></table></figure><h1 id="十一、网络编程基础"><a href="#十一、网络编程基础" class="headerlink" title="十一、网络编程基础"></a>十一、网络编程基础</h1><h2 id="1-1-网络编程概述"><a href="#1-1-网络编程概述" class="headerlink" title="1.1 网络编程概述"></a>1.1 网络编程概述</h2><p> 计算机网络</p><ul><li>是指将地理位置不同的具有独立功能的多台计算机及其外部设备，通过通信线路连接起来，在网络操作<br> 系统，网络管理软件及网络通信协议的管理和协调下，实现资源共享和信息传递的计算机系统</li></ul><p> 网络编程</p><ul><li>在网络通信协议下，实现网络互连的不同计算机上运行的程序间可以进行数据交换</li></ul><h2 id="1-2-网络编程三要素"><a href="#1-2-网络编程三要素" class="headerlink" title="1.2 网络编程三要素"></a>1.2 网络编程三要素</h2><ol><li><strong>IP地址</strong></li></ol><ul><li>要想让网络中的计算机能够互相通信，必须为每台计算机指定一个标识号，通过这个标识号来指定要接收数<br> 据的计算机和识别发送的计算机，而IP地址就是这个标识号。也就是设备的标识</li></ul><ol><li><strong>端口</strong></li></ol><ul><li>网络的通信，本质上是两个应用程序的通信。每台计算机都有很多的应用程序，那么在网络通信时，如何区<br> 分这些应用程序呢？如果说IP地址可以唯一标识网络中的设备，那么端口号就可以唯一标识设备中的应用程序<br> 了。也就是应用程序的标识</li></ul><ol><li><strong>通信协议</strong></li></ol><ul><li>通过计算机网络可以使多台计算机实现连接，位于同一个网络中的计算机在进行连接和通信时需要遵守一定<br> 的规则，这就好比在道路中行驶的汽车一定要遵守交通规则一样。在计算机网络中，这些连接和通信的规则<br> 被称为网络通信协议，它对数据的传输格式、传输速率、传输步骤等做了统一规定，通信双方必须同时遵守<br> 才能完成数据交换。常见的协议有UDP协议和TCP协议</li></ul><h2 id="1-3-IP地址"><a href="#1-3-IP地址" class="headerlink" title="1.3 IP地址"></a>1.3 IP地址</h2><p>IP地址：是网络中设备的唯一标识</p><p>IP地址分为两大类</p><ul><li>IPv4：是给每个连接在网络上的主机分配一个32bit地址。按照TCP/IP规定，IP地址用二进制来表示，每个IP地址长<br> 32bit，也就是4个字节。例如一个采用二进制形式的IP地址是“110000001010100000000001 01000010”，这么长<br> 的地址，处理起来也太费劲了。为了方便使用，IP地址经常被写成十进制的形式，中间使用符号“.”分隔不同的字节。<br> 于是，上面的IP地址可以表示为“192.168.1.66”。IP地址的这种表示法叫做“点分十进制表示法”，这显然比1和0容<br> 易记忆得多</li><li>由于互联网的蓬勃发展，IP地址的需求量愈来愈大，但是网络地址资源有限，使得IP的分配越发紧张。为了扩大<br> 地址空间，通过IPv6重新定义地址空间，采用128位地址长度，每16个字节一组，分成8组十六进制数，这样就解决了网络地址资源数量不够的问题</li></ul><p>常用命令</p><ul><li>ipconfig：查看本机IP地址</li><li>ping IP地址：检查网络是否连通</li></ul><p>特使IP地址：</p><ul><li>127.0.0.1：回送地址，可以代表本机，一般用来测试</li></ul><h2 id="1-4-InerAddress的使用"><a href="#1-4-InerAddress的使用" class="headerlink" title="1.4 InerAddress的使用"></a>1.4 InerAddress的使用</h2><p>为了方便我们对IP地址的获取和操作, Java提供了一个类InetAddress供我们使用</p><ul><li><p>InetAddress:此类表示Internet协议（IP）地址</p><p> <img src="D:\typoraImages\uTools_1638448531651.png" alt="uTools_1638448531651"></p></li></ul><h2 id="1-5-端口"><a href="#1-5-端口" class="headerlink" title="1.5 端口"></a>1.5 端口</h2><p>端口：设备上应用程序的唯一标识</p><p>端口号：用两个字节表示的整数，它的取值范围是0~65535。其中，0～1023之间的端口号用于一些知名的网<br>络服务和应用，普通的应用程序需要使用1024以上的端口号。如果端口号被另外一个服务或应用所占用，会导<br>致当前程序启动失败</p><h2 id="1-6-协议"><a href="#1-6-协议" class="headerlink" title="1.6 协议"></a>1.6 协议</h2><p>协议：计算机网络中，连接和通信的规则被称为网络通信协议</p><p><span style="color: red"><strong>UDP协议</strong></span></p><ul><li>用户数据报协议(User Datagram Protocol)</li><li>UDP是无连接通信协议，即在数据传输时，数据的发送端和接收端不建立逻辑连接。简单来说，当一台计算机向另外一台计算机发送数据时，发送端不会确认接收端是否存在，就会发出数据，同样接收端在收到数据时，也不会向发送端反馈是否收到数据。</li><li>由于使用UDP协议消耗资源小，通信效率高，所以通常都会用于音频、视频和普通数据的传输</li><li>例如视频会议通常采用UDP协议，因为这种情况即使偶尔丢失一两个数据包，也不会对接收结果产生太大影响。但是在使用UDP协议传送数据时，由于UDP的面向无连接性，不能保证数据的完整性，因此在传输重要数据时不建议使用UDP协议</li></ul><p><span style="color: red"><strong>TCP协议</strong></span></p><ul><li><p>传输控制协议（Transmission Control Protocol）</p></li><li><p>TCP协议是<span style="color:red">面向连接</span>的通信协议，即传输数据之前，在发送端和接收端建立逻辑连接，然后再传输数据，<br> 它提供了两台计算机之间<span style="color:red">可靠无差错</span>的数据传输。在TCP连接中必须要明确客户端与服务器端，由客户端<br> 向服务端发出连接请求，每次连接的创建都需要经过“三次握手。</p></li><li><p>三次握手：TCP协议中，在发送数据的准备阶段客户端与服务端之间的三次交互，以保证连接的可靠</p><ul><li><p>第一次握手，客户端向服务器端发出连接请求，等待服务器确认</p></li><li><p>第二次握手，服务器端向客户端回送一个响应，通知客户端收到了连接请求</p></li><li><p>第三次握手，客户端再次向服务器端发送确认信息，确认连接</p><ul><li>完成三次握手，连接建立后，客户端和服务器就可以开始进行数据传输了。这种面向连接的特性,TCP协议可以保证传输数据的安全，所以应用十分广泛。例如上传文件、下载文件、浏览网页等</li></ul></li></ul></li></ul><h2 id="2-UDP通信程序"><a href="#2-UDP通信程序" class="headerlink" title="2. UDP通信程序"></a>2. UDP通信程序</h2><h5 id="2-1-UDP通信原理"><a href="#2-1-UDP通信原理" class="headerlink" title="2.1 UDP通信原理"></a>2.1 UDP通信原理</h5><p>UDP协议是一种不可靠的网络协议，它在通信的两端各建立一个Socket对象，但是这两个Socket只是发送，接收数据的对象</p><p>因此对于基于UDP协议的通信双方而言，没有所谓的客户端和服务器的概念</p><p>Java提供了DatagramSocket类作为基于UDP协议的Socket</p><h5 id="2-2-UDP发送数据"><a href="#2-2-UDP发送数据" class="headerlink" title="2.2 UDP发送数据"></a>2.2 UDP发送数据</h5><p>发送数据的步骤</p><ol><li>创建发送端的Socket对象(DatagramSocket)</li><li>创建数据，并把数据打包</li><li>调用DatagramSocket对象的方法发送数据</li><li>关闭发送端</li></ol><p>发送数据的步骤<br>① 创建发送端的Socket对象(DatagramSocket)<br> DatagramSocket()<br>② 创建数据，并把数据打包<br> DatagramPacket(byte[] buf, int length, InetAddress address, int port)<br>③ 调用DatagramSocket对象的方法发送数据<br> void send(DatagramPacket p)<br>④ 关闭发送端<br> void close()</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.itheima.MyNet.itheima02;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> java.io.IOException;</span><br><span class="line"><span class="keyword">import</span> java.net.*;</span><br><span class="line"><span class="keyword">import</span> java.nio.charset.StandardCharsets;</span><br><span class="line"></span><br><span class="line"><span class="comment">/*</span></span><br><span class="line"><span class="comment"> 1. 创建发送端的Socket对象(DatagramSocket)</span></span><br><span class="line"><span class="comment"> 2. 创建数据，并把数据打包</span></span><br><span class="line"><span class="comment"> 3. 调用DatagramSocket对象的方法发送数据</span></span><br><span class="line"><span class="comment"> 4. 关闭发送端</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">SendDemo</span> {</span><br><span class="line"> <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> IOException {</span><br><span class="line"> <span class="comment">// 创建发送端的Socket对象(DatagramSocket)</span></span><br><span class="line"> <span class="comment">// 构造方法：DatagramSocket() 构造数据报套接字并将其绑定到本地主机上的任何可用端口。</span></span><br><span class="line"> <span class="type">DatagramSocket</span> <span class="variable">ds</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">DatagramSocket</span>(<span class="number">3306</span>);</span><br><span class="line"></span><br><span class="line"> <span class="comment">// 创建数据，并把数据打包</span></span><br><span class="line"> <span class="comment">// DatagramPacket(byte[] buf, int length, InetAddress address, int port)</span></span><br><span class="line"> <span class="comment">// 构造一个数据包，发送长度为 length的数据包到指定主机上的指定端口号。</span></span><br><span class="line"> <span class="type">byte</span>[] bytes = <span class="string">"大头大头"</span>.getBytes();</span><br><span class="line"><span class="comment">// int len = bytes.length;</span></span><br><span class="line"><span class="comment">// InetAddress address = InetAddress.getByName("10.102.57.46");</span></span><br><span class="line"><span class="comment">// int port = 12345;</span></span><br><span class="line"> <span class="type">DatagramPacket</span> <span class="variable">dp</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">DatagramPacket</span>(bytes, bytes.length,InetAddress.getByName(<span class="string">"2409:8a30:8a43:2240:5ef:bf78:eccc:4d5"</span>),<span class="number">1219</span>);</span><br><span class="line"></span><br><span class="line"></span><br><span class="line"> <span class="comment">// 调用DatagramSocket对象的方法发送数据</span></span><br><span class="line"> ds.send(dp);</span><br><span class="line"></span><br><span class="line"> <span class="comment">// 关闭发送端</span></span><br><span class="line"> ds.close();</span><br><span class="line"></span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure><h5 id="2-3-UDP接受数据"><a href="#2-3-UDP接受数据" class="headerlink" title="2.3 UDP接受数据"></a>2.3 UDP接受数据</h5><p>接收数据的步骤<br>① 创建接收端的Socket对象(DatagramSocket)<br>② 创建一个数据包，用于接收数据<br>③ 调用DatagramSocket对象的方法接收数据<br>④ 解析数据包，并把数据在控制台显示关闭接收端</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.itheima.MyNet.itheima02;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> java.io.IOException;</span><br><span class="line"><span class="keyword">import</span> java.net.DatagramPacket;</span><br><span class="line"><span class="keyword">import</span> java.net.DatagramSocket;</span><br><span class="line"><span class="keyword">import</span> java.net.SocketException;</span><br><span class="line"><span class="keyword">import</span> java.util.Arrays;</span><br><span class="line"></span><br><span class="line"><span class="comment">/*</span></span><br><span class="line"><span class="comment"> 接收数据的步骤</span></span><br><span class="line"><span class="comment"> 1. 创建接收端的Socket对象(DatagramSocket)</span></span><br><span class="line"><span class="comment"> 2. 创建一个数据包，用于接收数据</span></span><br><span class="line"><span class="comment"> 3. 调用DatagramSocket对象的方法接收数据</span></span><br><span class="line"><span class="comment"> 4. 解析数据包，并把数据在控制台显示关闭接收端</span></span><br><span class="line"><span class="comment"> 5. 关闭接收端</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">ReceiveDemo</span> {</span><br><span class="line"> <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> IOException {</span><br><span class="line"> <span class="keyword">while</span>(<span class="literal">true</span>) {</span><br><span class="line"> <span class="comment">// 创建接收端的Socket对象(DatagramSocket)</span></span><br><span class="line"> <span class="type">DatagramSocket</span> <span class="variable">ds</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">DatagramSocket</span>(<span class="number">1219</span>);</span><br><span class="line"></span><br><span class="line"> <span class="comment">// 创建一个数据包，用于接收数据</span></span><br><span class="line"> <span class="type">byte</span>[] bys = <span class="keyword">new</span> <span class="title class_">byte</span>[<span class="number">1024</span>];</span><br><span class="line"> <span class="type">DatagramPacket</span> <span class="variable">dp</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">DatagramPacket</span>(bys, bys.length);</span><br><span class="line"></span><br><span class="line"> <span class="comment">// 调用DatagramSocket对象的方法接收数据</span></span><br><span class="line"> ds.receive(dp);</span><br><span class="line"></span><br><span class="line"> <span class="comment">// 解析数据包，并把数据在控制台显示关闭接收端</span></span><br><span class="line"> <span class="type">byte</span>[] data = dp.getData();</span><br><span class="line"> <span class="type">int</span> <span class="variable">len</span> <span class="operator">=</span> dp.getLength();</span><br><span class="line"> <span class="type">String</span> <span class="variable">dataString</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">String</span>(data,<span class="number">0</span>,len);</span><br><span class="line"> System.out.println(<span class="string">"数据是："</span> + dataString);</span><br><span class="line"></span><br><span class="line"> <span class="comment">// 关闭接收端</span></span><br><span class="line"> ds.close();</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure><h4 id="3-TCP通信程序"><a href="#3-TCP通信程序" class="headerlink" title="3. TCP通信程序"></a>3. TCP通信程序</h4><h5 id="3-1-TCP通信原理"><a href="#3-1-TCP通信原理" class="headerlink" title="3.1 TCP通信原理"></a>3.1 TCP通信原理</h5><p>TCP通信协议是一种可靠的网络协议，它在通信的两端各建立一个Socket对象，从而在通信的两端形成网络虚拟链路，一旦建立了虚拟的网络链路，两端的程序就可过虚拟链路进行通信</p><p>Java对基于TCP协议的网络提供了良好的封装，使用Socket对象来表示两端的通信端口，并通过Socket产生IO流来进行网络通信，Java为客户端提供了Socket类，为服务器端提供了ServerSocket类</p><p><img src="D:\typoraImages\uTools_1638448732396.png" alt="uTools_1638448732396"></p><h5 id="3-2-TCP发送数据"><a href="#3-2-TCP发送数据" class="headerlink" title="3.2 TCP发送数据"></a>3.2 TCP发送数据</h5><p>发送数据的步骤<br>① 创建客户端的Socket对象(Socket)</p><p> Socket(String host, int ]port)</p><p>② 获取输出流，写数据</p><p> OutPutStream getOutPutStream()</p><p>③ 释放资源</p><p> void close()</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.itheima.MyNet.itheima04;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> java.io.*;</span><br><span class="line"><span class="keyword">import</span> java.net.InetAddress;</span><br><span class="line"><span class="keyword">import</span> java.net.Socket;</span><br><span class="line"></span><br><span class="line"><span class="comment">/*</span></span><br><span class="line"><span class="comment"> TCP发送数据的步骤</span></span><br><span class="line"><span class="comment"> ① 创建客户端的Socket对象(Socket)</span></span><br><span class="line"><span class="comment"> ② 获取输出流，写数据</span></span><br><span class="line"><span class="comment"> ③ 释放资源</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">ClientDemo</span> {</span><br><span class="line"> <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> IOException {</span><br><span class="line"> <span class="comment">//创建客户端的Socket对象(Socket)</span></span><br><span class="line"> <span class="comment">//Socket(InetAddress address, int port) 创建流套接字并将其连接到指定IP地址的指定端口号。</span></span><br><span class="line"><span class="comment">// Socket s = new Socket(InetAddress.getByName("10.102.57.46"),3306);</span></span><br><span class="line"> <span class="comment">//Socket(String host, int port) 创建流套接字并将其连接到指定主机上的指定端口号。</span></span><br><span class="line"> <span class="type">Socket</span> <span class="variable">s</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Socket</span>(<span class="string">"10.102.57.46"</span>, <span class="number">3306</span>);</span><br><span class="line"></span><br><span class="line"> <span class="comment">//获取输出流，写数据</span></span><br><span class="line"> <span class="comment">//OutputStream getOutputStream() 返回此套接字的输出流。</span></span><br><span class="line"> <span class="type">OutputStream</span> <span class="variable">os</span> <span class="operator">=</span> s.getOutputStream();</span><br><span class="line"> os.write(<span class="string">"这是tcp协议发送的数据"</span>.getBytes());</span><br><span class="line"></span><br><span class="line"> <span class="comment">//释放资源</span></span><br><span class="line"> s.close();</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure><h5 id="3-3-TCP接收数据"><a href="#3-3-TCP接收数据" class="headerlink" title="3.3 TCP接收数据"></a>3.3 TCP接收数据</h5><p>接收数据的步骤<br>① 创建服务器端的Socket对象(ServerSocket)<br> ServerSocket(int port)<br>②监听客户端连接，返回一个Socket对象<br> Socket accept()<br>③获取输入流，读数据，并把数据显示在控制台<br> InputStream getInputStream()<br>④释放资源<br> void close()</p><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.itheima.MyNet.itheima04;</span><br><span class="line"></span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> java.io.IOException;</span><br><span class="line"><span class="keyword">import</span> java.io.InputStream;</span><br><span class="line"><span class="keyword">import</span> java.net.ServerSocket;</span><br><span class="line"><span class="keyword">import</span> java.net.Socket;</span><br><span class="line"></span><br><span class="line"><span class="comment">/*</span></span><br><span class="line"><span class="comment"> 接收数据的步骤</span></span><br><span class="line"><span class="comment"> ① 创建服务器端的Socket对象(ServerSocket)</span></span><br><span class="line"><span class="comment"> ② 获取输入流，读数据，并把数据显示在控制台</span></span><br><span class="line"><span class="comment"> ③ 释放资源</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">ServerDemo</span> {</span><br><span class="line"> <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> IOException {</span><br><span class="line"> <span class="comment">//创建服务器端的Socket对象(ServerSocket)</span></span><br><span class="line"> <span class="type">ServerSocket</span> <span class="variable">serverSocket</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">ServerSocket</span>(<span class="number">7000</span>);</span><br><span class="line"></span><br><span class="line"> <span class="comment">//Socket accept() 侦听要连接到此套接字并接受它。</span></span><br><span class="line"> <span class="type">Socket</span> <span class="variable">accept</span> <span class="operator">=</span> serverSocket.accept();</span><br><span class="line"></span><br><span class="line"> <span class="comment">//获取输入流，读数据，并把数据显示在控制台</span></span><br><span class="line"> <span class="type">InputStream</span> <span class="variable">inputStream</span> <span class="operator">=</span> accept.getInputStream();</span><br><span class="line"> <span class="type">byte</span>[] bys = <span class="keyword">new</span> <span class="title class_">byte</span>[<span class="number">1024</span>];</span><br><span class="line"> <span class="type">int</span> <span class="variable">len</span> <span class="operator">=</span> inputStream.read(bys);</span><br><span class="line"> <span class="type">String</span> <span class="variable">data</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">String</span>(bys, <span class="number">0</span>, len);</span><br><span class="line"> System.out.println(<span class="string">"数据是："</span> + data);</span><br><span class="line"></span><br><span class="line"></span><br><span class="line"> <span class="comment">//释放资源</span></span><br><span class="line"> serverSocket.close();</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure><h1 id="十二、Lambda表达式"><a href="#十二、Lambda表达式" class="headerlink" title="十二、Lambda表达式"></a>十二、Lambda表达式</h1><h2 id="1-1-函数式编程思想概述"><a href="#1-1-函数式编程思想概述" class="headerlink" title="1.1 函数式编程思想概述"></a>1.1 函数式编程思想概述</h2><p><img src="D:\typoraImages\uTools_1639396954033.png" alt="uTools_1639396954033"></p><p>在数学中，函数就是有输入量、输出量的一套计算方案，也就是“拿数据做操作”<br>面向对象思想强调“必须通过对象的形式来做事情”<br>函数式思想则尽量忽略面向对象的复杂语法“强调做什么，而不是以什么形式去做”<br>而我们要学习的Lambda表达式就是函数式思想的体现</p><h4 id="1-2-体验Lambda表达式"><a href="#1-2-体验Lambda表达式" class="headerlink" title="1.2 体验Lambda表达式"></a>1.2 体验Lambda表达式</h4><p>需求：启动一个线程，在控制台输出—句话：多线程程序启动了</p><p>方式1:</p><ul><li>定义一个类MyRunnable实现Runnable接口，重写run()方法</li><li>创建MyRunnable类的对象</li><li>创建Thread类的对象，把MyRunnable的对象作为构造参数传递</li><li>启动线程</li></ul><h1 id="javaWeb介绍"><a href="#javaWeb介绍" class="headerlink" title="javaWeb介绍"></a>javaWeb介绍</h1><p><strong>什么时javaWeb？</strong></p><ul><li>Web：全球广域网，也称为万维网(www)，能够通过浏览器访问的<span style="color:red">网站</span></li><li>JavaWeb：是用Java技术来解决相关web互联网领域的技术栈</li></ul><h1 id="十三、正则表达式"><a href="#十三、正则表达式" class="headerlink" title="十三、正则表达式"></a>十三、正则表达式</h1><p>正则表达式定义了字符串组成的规则</p><p>定义：</p><figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">var</span> reg = <span class="regexp">/^\w{6,12}$/</span>; <span class="comment">//不要加引号</span></span><br></pre></td></tr></table></figure><p>方法：</p><ul><li>test(str)：判断指定字符串是否符合规则，返回true或false</li></ul><h2 id="语法"><a href="#语法" class="headerlink" title="语法"></a>语法</h2><ul><li>^：开始</li><li>$：结束</li><li>[ ]：代表某个范围内的单个字符,如：[0-9] 单个数字字符</li><li>.：代表任意单个字符，除了换行和行结束符</li><li>\w：代表单词字符：字母、数字、下划线（<em>_</em>），相当于[A-Z a-z 0-9<em>_</em>]</li><li>\d：代表数字字符：相当于[0-9]</li><li>量词：</li><li>+：至少一个</li><li>*：零个或多个</li><li>？：零个或一个</li><li>{x}：x个</li><li>{m,}：至少m个</li><li>{m,n}：至少m个，最多n个<!-- markdownlint-disable MD025 --><h1 id="二十、Web核心"><a href="#二十、Web核心" class="headerlink" title="二十、Web核心"></a>二十、Web核心</h1></li></ul><h2 id="一、javaWeb技术栈"><a href="#一、javaWeb技术栈" class="headerlink" title="一、javaWeb技术栈"></a>一、javaWeb技术栈</h2><ul><li>B/S架构：Browser/Server，浏览器/服务器 架构模式，它的特点是，客户端只需要浏览器，应用程序的逻辑和数<br> 据都存储在服务器端。浏览器只需要请求服务器，获取Web资源，服务器把Web资源发送给浏览器即可<!-- markdownlint-disable MD001 --><h4 id="二、HTTP"><a href="#二、HTTP" class="headerlink" title="二、HTTP"></a>二、HTTP</h4></li></ul><h5 id="1-1-概念"><a href="#1-1-概念" class="headerlink" title="1.1 概念"></a>1.1 概念</h5><ul><li>HyperText Transfer Protocol，超文本传输协议，规定了浏览器和服务器之间数据传输的规则</li></ul><h5 id="1-2-HTTP协议特点"><a href="#1-2-HTTP协议特点" class="headerlink" title="1.2 HTTP协议特点"></a>1.2 HTTP协议特点</h5><ol><li>基于TCP协议：面向连接，安全</li><li>基于请求-响应模型的：一次请求对应一次响应</li><li>HTTP协议是无状态的协议：对于事务处理没有记忆能力。每次请求-响应都是独立的。</li></ol><ul><li>缺点：多次请求间不能共享数据。Java中使用会话技术(Cookie、Session）来解决这个问题</li><li>优点：速度快</li></ul><h5 id="1-3-HTTP-请求数据格式‘"><a href="#1-3-HTTP-请求数据格式‘" class="headerlink" title="1.3 HTTP-请求数据格式‘"></a>1.3 HTTP-请求数据格式‘</h5><!-- markdownlint-disable MD033 --><p>请求数据分为3部分：<br><span style="color:red">1.请求行</span>：请求数据的第一行。其中GET表示请求方式，/表示请求资源路径，HTTP/1.1表示协议版本<br><span style="color:red">2.请求头</span>：第二行开始，格式为key：value形式。<br><span style="color:red">3.请求体</span>：POST请求的最后一部分，存放请求参数</p><p><img src="D:\typoraImages\uTools_1639998349113.png" alt="uTools_1639998349113"></p><p>常见的HTTP 请求头：</p><ul><li><p>Host: 表示请求的主机名</p></li><li><p>User-Agent: 浏览器版本，例如Chrome浏览器的标识类似Mozilla/5.0</p><p> Chrome/79，IE浏览器的标识类似Mozilla/5.0 (Windows NT …) like Gecko；</p></li><li><p>Accept：表示浏览器能接收的资源类型，如text/<em>，image/</em>或者<em>/</em>表示所有；</p></li><li><p>Accept-Language：表示浏览器偏好的语言，服务器可以据此返回不同语言的网页；</p></li><li><p>Accept-Encoding：表示浏览器可以支持的压缩类型，例如gzip, deflate等。</p></li></ul><p><img src="D:\typoraImages\uTools_1639998597810.png" alt="uTools_1639998597810"></p><p>GET请求和 POST请求区别：</p><ol><li>GET请求请求参数在请求行中，没有请求体。<pre><code>POST请求请求参数在请求体中</code></pre></li><li>2.GET请求请求参数大小有限制，<pre><code>POST没有</code></pre></li></ol><h5 id="1-HTTP-响应数据格式"><a href="#1-HTTP-响应数据格式" class="headerlink" title="1. HTTP-响应数据格式"></a>1. HTTP-响应数据格式</h5><!-- markdownlint-disable MD033 --><p>响应数据分为3部分：<br><span style="color:red">1.响应行</span>： 响应数据的第一行。其中HTTP/1.1表示协议版本， 200表示响应状态码，OK表示状态码描述<br><span style="color:red">2.响应头</span>： 第二行开始，格式为key：value形式<br><span style="color:red">3.响应体</span>： 最后一部分。存放响应数据</p><p><img src="D:\typoraImages\uTools_1639998972904.png" alt="uTools_1639998972904"></p><p><img src="D:\typoraImages\uTools_1639999011417.png" alt="uTools_1639999011417"></p><p>常见的HTTP 响应头：<br>Content-Type:表示该响应内容的类型，例如text/html，image/jpeg;<br>Content-Length：表示该响应内容的长度（字节数) ;<br>Content-Encoding:表示该响应压缩算法，例如gzip;<br>Cache-Control：指示客户端应如何缓存，例如max-age=300,表示可以最多缓存300秒</p><ul><li>Web服务器是一个应该程序（软件），对HTTP协议的操作进行封装，使得程序员不必直接对协议进行操作，让Web开<br> 发更加便捷。主要功能是“提供网上信息浏览服务“</li></ul><p><img src="D:\typoraImages\uTools_1639999691337.png" alt="uTools_1639999691337"></p><h4 id="1-5-Tomcat"><a href="#1-5-Tomcat" class="headerlink" title="1.5 Tomcat"></a>1.5 Tomcat</h4><p>概念：</p><ul><li><p>Tomcat是Apache软件基金会一个核心项目，是一个开源免费的轻量级Web服务器，支持Servlet/JSP，少量JavaEE规范。</p></li><li><p>JavaEE:Java Enterprise Edition，Java企业版。指Java企业级开发的技术规范总和。包含13项JDBC、JNDI、EJB、RMI、JSP、Servlet、XML、JMS、Java IDL、JTS、JTA、JavaMail、JAF</p></li><li><p>Tomcat也被称为Web容器、Servlet容器。Servlet需要依赖于Tomcat才能运行</p></li></ul><h4 id="总结"><a href="#总结" class="headerlink" title="总结"></a>总结</h4><ol><li>Web 服务器作用？<ul><li>封装HTTP协议操作，简化开发</li><li>可以将web项目部署到服务器中，对外提供网上浏览服务</li></ul></li><li>Tomcat是一个轻量级的Web服务器，支持Servlet/JSP少量<br>JavaEE规范，也称为Web容器，Servlet容器<br>3.<!-- markdownlint-disable MD025 --><h1 id="二十一、IDEA中创建Maven-Web项目"><a href="#二十一、IDEA中创建Maven-Web项目" class="headerlink" title="二十一、IDEA中创建Maven Web项目"></a>二十一、IDEA中创建Maven Web项目</h1></li></ol><ul><li>Web项目构建</li></ul><p><img src="D:\typoraImages\uTools_1640004314147.png" alt="uTools_1640004314147"></p><p><img src="D:\typoraImages\uTools_1640004353879.png" alt="uTools_1640004353879"></p><ul><li>使用骨架创建</li></ul><p><img src="D:\typoraImages\uTools_1640087139632.png" alt="uTools_1640087139632"></p><ul><li>不使用骨架创建</li></ul><p><img src="C:\Users\30697\AppData\Roaming\Typora\typora-user-images\image-20211221195858886.png" alt="image-20211221195858886"></p><p><img src="C:\Users\30697\AppData\Roaming\Typora\typora-user-images\image-20211221200119441.png" alt="image-20211221200119441"><br><!-- markdownlint-disable MD033 --><br><img src="C:\Users\30697\AppData\Roaming\Typora\typora-user-images\image-20211221200217093.png" alt="image-20211221200217093" style="zoom:75%;" /></p><p><img src="C:\Users\30697\AppData\Roaming\Typora\typora-user-images\image-20211221200352792.png" alt="image-20211221200352792"></p><p><img src="C:\Users\30697\AppData\Roaming\Typora\typora-user-images\image-20211221200539688.png" alt="image-20211221200539688"></p><p><img src="C:\Users\30697\AppData\Roaming\Typora\typora-user-images\image-20211221200608894.png" alt="image-20211221200608894"><br><!-- markdownlint-disable MD025 --></p><h1 id="二十二、IDEA中使用Tomcat"><a href="#二十二、IDEA中使用Tomcat" class="headerlink" title="二十二、IDEA中使用Tomcat"></a>二十二、IDEA中使用Tomcat</h1><ul><li>将本地Tomcat集成到IDEA中，然后进行项目部署</li></ul><p><img src="D:\typoraImages\uTools_1640086097462.png" alt="uTools_1640086097462"></p><ul><li>Tomcat Maven 插件</li></ul>]]></content>
<categories>
<category> 编程 </category>
</categories>
<tags>
<tag> Java基础 </tag>
</tags>
</entry>
<entry>
<title>Mysql学习笔记！</title>
<link href="/posts/1.html"/>
<url>/posts/1.html</url>
<content type="html"><![CDATA[<!-- markdownlint-disable MD025 --><h1 id="MySQL学习笔记"><a href="#MySQL学习笔记" class="headerlink" title="MySQL学习笔记"></a>MySQL学习笔记</h1><h2 id="登录和退出MySQL服务器"><a href="#登录和退出MySQL服务器" class="headerlink" title="登录和退出MySQL服务器"></a>登录和退出MySQL服务器</h2><figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta prompt_"># </span><span class="language-bash">登录MySQL</span></span><br><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">mysql -u root -p12345612</span></span><br><span class="line"><span class="meta prompt_"></span></span><br><span class="line"><span class="meta prompt_"># </span><span class="language-bash">退出MySQL数据库服务器</span></span><br><span class="line">exit;</span><br></pre></td></tr></table></figure><h2 id="基本语法"><a href="#基本语法" class="headerlink" title="基本语法"></a>基本语法</h2><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br></pre></td><td class="code"><pre><span class="line">-- 显示所有数据库</span><br><span class="line">show databases;</span><br><span class="line"></span><br><span class="line">-- 创建数据库</span><br><span class="line">CREATE DATABASE test;</span><br><span class="line"></span><br><span class="line">-- 切换数据库</span><br><span class="line">use test;</span><br><span class="line"></span><br><span class="line">-- 显示数据库中的所有表</span><br><span class="line">show tables;</span><br><span class="line"></span><br><span class="line">-- 创建数据表</span><br><span class="line">CREATE TABLE pet (</span><br><span class="line"> name VARCHAR(20),</span><br><span class="line"> owner VARCHAR(20),</span><br><span class="line"> species VARCHAR(20),</span><br><span class="line"> sex CHAR(1),</span><br><span class="line"> birth DATE,</span><br><span class="line"> death DATE</span><br><span class="line">);</span><br><span class="line"></span><br><span class="line">-- 查看数据表结构</span><br><span class="line">-- describe pet;</span><br><span class="line">desc pet;</span><br><span class="line"></span><br><span class="line">-- 查询表</span><br><span class="line">SELECT * from pet;</span><br><span class="line"></span><br><span class="line">-- 插入数据</span><br><span class="line">INSERT INTO pet VALUES ('puffball', 'Diane', 'hamster', 'f', '1990-03-30', NULL);</span><br><span class="line"></span><br><span class="line">-- 修改数据</span><br><span class="line">UPDATE pet SET name = 'squirrel' where owner = 'Diane';</span><br><span class="line"></span><br><span class="line">-- 删除数据</span><br><span class="line">DELETE FROM pet where name = 'squirrel';</span><br><span class="line"></span><br><span class="line">-- 删除表</span><br><span class="line">DROP TABLE myorder;</span><br></pre></td></tr></table></figure><h2 id="建表约束"><a href="#建表约束" class="headerlink" title="建表约束"></a>建表约束</h2><h3 id="主键约束"><a href="#主键约束" class="headerlink" title="主键约束"></a>主键约束</h3><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br></pre></td><td class="code"><pre><span class="line">-- 主键约束</span><br><span class="line">-- 使某个字段不重复且不得为空，确保表内所有数据的唯一性。</span><br><span class="line">CREATE TABLE user (</span><br><span class="line"> id INT PRIMARY KEY,</span><br><span class="line"> name VARCHAR(20)</span><br><span class="line">);</span><br><span class="line"></span><br><span class="line">-- 联合主键</span><br><span class="line">-- 联合主键中的每个字段都不能为空，并且加起来不能和已设置的联合主键重复。</span><br><span class="line">CREATE TABLE user (</span><br><span class="line"> id INT,</span><br><span class="line"> name VARCHAR(20),</span><br><span class="line"> password VARCHAR(20),</span><br><span class="line"> PRIMARY KEY(id, name)</span><br><span class="line">);</span><br><span class="line"></span><br><span class="line">-- 自增约束</span><br><span class="line">-- 自增约束的主键由系统自动递增分配。</span><br><span class="line">CREATE TABLE user (</span><br><span class="line"> id INT PRIMARY KEY AUTO_INCREMENT,</span><br><span class="line"> name VARCHAR(20)</span><br><span class="line">);</span><br><span class="line"></span><br><span class="line">-- 添加主键约束</span><br><span class="line">-- 如果忘记设置主键，还可以通过SQL语句设置（两种方式）：</span><br><span class="line">ALTER TABLE user ADD PRIMARY KEY(id);</span><br><span class="line">ALTER TABLE user MODIFY id INT PRIMARY KEY;</span><br><span class="line"></span><br><span class="line">-- 删除主键</span><br><span class="line">ALTER TABLE user drop PRIMARY KEY;</span><br></pre></td></tr></table></figure><h3 id="唯一主键"><a href="#唯一主键" class="headerlink" title="唯一主键"></a>唯一主键</h3><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line">-- 建表时创建唯一主键</span><br><span class="line">CREATE TABLE user (</span><br><span class="line"> id INT,</span><br><span class="line"> name VARCHAR(20),</span><br><span class="line"> UNIQUE(name)</span><br><span class="line">);</span><br><span class="line"></span><br><span class="line">-- 添加唯一主键</span><br><span class="line">-- 如果建表时没有设置唯一建，还可以通过SQL语句设置（两种方式）：</span><br><span class="line">ALTER TABLE user ADD UNIQUE(name);</span><br><span class="line">ALTER TABLE user MODIFY name VARCHAR(20) UNIQUE;</span><br><span class="line"></span><br><span class="line">-- 删除唯一主键</span><br><span class="line">ALTER TABLE user DROP INDEX name;</span><br></pre></td></tr></table></figure><h3 id="非空约束"><a href="#非空约束" class="headerlink" title="非空约束"></a>非空约束</h3><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line">-- 建表时添加非空约束</span><br><span class="line">-- 约束某个字段不能为空</span><br><span class="line">CREATE TABLE user (</span><br><span class="line"> id INT,</span><br><span class="line"> name VARCHAR(20) NOT NULL</span><br><span class="line">);</span><br><span class="line"></span><br><span class="line">-- 移除非空约束</span><br><span class="line">ALTER TABLE user MODIFY name VARCHAR(20);</span><br></pre></td></tr></table></figure><h3 id="默认约束"><a href="#默认约束" class="headerlink" title="默认约束"></a>默认约束</h3><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line">-- 建表时添加默认约束</span><br><span class="line">-- 约束某个字段的默认值</span><br><span class="line">CREATE TABLE user2 (</span><br><span class="line"> id INT,</span><br><span class="line"> name VARCHAR(20),</span><br><span class="line"> age INT DEFAULT 10</span><br><span class="line">);</span><br><span class="line"></span><br><span class="line">-- 移除非空约束</span><br><span class="line">ALTER TABLE user MODIFY age INT;</span><br></pre></td></tr></table></figure><h3 id="外键约束"><a href="#外键约束" class="headerlink" title="外键约束"></a>外键约束</h3><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br></pre></td><td class="code"><pre><span class="line">-- 班级</span><br><span class="line">CREATE TABLE classes (</span><br><span class="line"> id INT PRIMARY KEY,</span><br><span class="line"> name VARCHAR(20)</span><br><span class="line">);</span><br><span class="line"></span><br><span class="line">-- 学生表</span><br><span class="line">CREATE TABLE students (</span><br><span class="line"> id INT PRIMARY KEY,</span><br><span class="line"> name VARCHAR(20),</span><br><span class="line"> -- 这里的 class_id 要和 classes 中的 id 字段相关联</span><br><span class="line"> class_id INT,</span><br><span class="line"> -- 表示 class_id 的值必须来自于 classes 中的 id 字段值</span><br><span class="line"> FOREIGN KEY(class_id) REFERENCES classes(id)</span><br><span class="line">);</span><br><span class="line"></span><br><span class="line">-- 1. 主表（父表）classes 中没有的数据值，在副表（子表）students 中，是不可以使用的；</span><br><span class="line">-- 2. 主表中的记录被副表引用时，主表不可以被删除。</span><br></pre></td></tr></table></figure><h2 id="数据库的三大设计范式"><a href="#数据库的三大设计范式" class="headerlink" title="数据库的三大设计范式"></a>数据库的三大设计范式</h2><h3 id="1NF"><a href="#1NF" class="headerlink" title="1NF"></a>1NF</h3><p>只要字段值还可以继续拆分，就不满足第一范式。</p><p>范式设计得越详细，对某些实际操作可能会更好，但并非都有好处，需要对项目的实际情况进行设定。</p><h3 id="2NF"><a href="#2NF" class="headerlink" title="2NF"></a>2NF</h3><p>在满足第一范式的前提下，其他列都必须完全依赖于主键列。如果出现不完全依赖，只可能发生在联合主键的情况下：</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line">-- 订单表</span><br><span class="line">CREATE TABLE myorder (</span><br><span class="line"> product_id INT,</span><br><span class="line"> customer_id INT,</span><br><span class="line"> product_name VARCHAR(20),</span><br><span class="line"> customer_name VARCHAR(20),</span><br><span class="line"> PRIMARY KEY (product_id, customer_id)</span><br><span class="line">);</span><br></pre></td></tr></table></figure><p>实际上，在这张订单表中，<code>product_name</code> 只依赖于 <code>product_id</code> ，<code>customer_name</code> 只依赖于 <code>customer_id</code> 。也就是说，<code>product_name</code> 和 <code>customer_id</code> 是没用关系的，<code>customer_name</code> 和 <code>product_id</code> 也是没有关系的。</p><p>这就不满足第二范式：其他列都必须完全依赖于主键列！</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line">CREATE TABLE myorder (</span><br><span class="line"> order_id INT PRIMARY KEY,</span><br><span class="line"> product_id INT,</span><br><span class="line"> customer_id INT</span><br><span class="line">);</span><br><span class="line"></span><br><span class="line">CREATE TABLE product (</span><br><span class="line"> id INT PRIMARY KEY,</span><br><span class="line"> name VARCHAR(20)</span><br><span class="line">);</span><br><span class="line"></span><br><span class="line">CREATE TABLE customer (</span><br><span class="line"> id INT PRIMARY KEY,</span><br><span class="line"> name VARCHAR(20)</span><br><span class="line">);</span><br></pre></td></tr></table></figure><p>拆分之后，<code>myorder</code> 表中的 <code>product_id</code> 和 <code>customer_id</code> 完全依赖于 <code>order_id</code> 主键，而 <code>product</code> 和 <code>customer</code> 表中的其他字段又完全依赖于主键。满足了第二范式的设计！</p><h3 id="3NF"><a href="#3NF" class="headerlink" title="3NF"></a>3NF</h3><p>在满足第二范式的前提下，除了主键列之外，其他列之间不能有传递依赖关系。</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line">CREATE TABLE myorder (</span><br><span class="line"> order_id INT PRIMARY KEY,</span><br><span class="line"> product_id INT,</span><br><span class="line"> customer_id INT,</span><br><span class="line"> customer_phone VARCHAR(15)</span><br><span class="line">);</span><br></pre></td></tr></table></figure><p>表中的 <code>customer_phone</code> 有可能依赖于 <code>order_id</code> 、 <code>customer_id</code> 两列，也就不满足了第三范式的设计：其他列之间不能有传递依赖关系。</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line">CREATE TABLE myorder (</span><br><span class="line"> order_id INT PRIMARY KEY,</span><br><span class="line"> product_id INT,</span><br><span class="line"> customer_id INT</span><br><span class="line">);</span><br><span class="line"></span><br><span class="line">CREATE TABLE customer (</span><br><span class="line"> id INT PRIMARY KEY,</span><br><span class="line"> name VARCHAR(20),</span><br><span class="line"> phone VARCHAR(15)</span><br><span class="line">);</span><br></pre></td></tr></table></figure><p>修改后就不存在其他列之间的传递依赖关系，其他列都只依赖于主键列，满足了第三范式的设计！</p><h2 id="查询练习"><a href="#查询练习" class="headerlink" title="查询练习"></a>查询练习</h2><h3 id="准备数据"><a href="#准备数据" class="headerlink" title="准备数据"></a>准备数据</h3><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br><span class="line">73</span><br><span class="line">74</span><br><span class="line">75</span><br><span class="line">76</span><br><span class="line">77</span><br><span class="line">78</span><br><span class="line">79</span><br><span class="line">80</span><br><span class="line">81</span><br><span class="line">82</span><br><span class="line">83</span><br><span class="line">84</span><br><span class="line">85</span><br><span class="line">86</span><br><span class="line">87</span><br></pre></td><td class="code"><pre><span class="line">-- 创建数据库</span><br><span class="line">CREATE DATABASE select_test;</span><br><span class="line">-- 切换数据库</span><br><span class="line">USE select_test;</span><br><span class="line"></span><br><span class="line">-- 创建学生表</span><br><span class="line">CREATE TABLE student (</span><br><span class="line"> no VARCHAR(20) PRIMARY KEY,</span><br><span class="line"> name VARCHAR(20) NOT NULL,</span><br><span class="line"> sex VARCHAR(10) NOT NULL,</span><br><span class="line"> birthday DATE, -- 生日</span><br><span class="line"> class VARCHAR(20) -- 所在班级</span><br><span class="line">);</span><br><span class="line"></span><br><span class="line">-- 创建教师表</span><br><span class="line">CREATE TABLE teacher (</span><br><span class="line"> no VARCHAR(20) PRIMARY KEY,</span><br><span class="line"> name VARCHAR(20) NOT NULL,</span><br><span class="line"> sex VARCHAR(10) NOT NULL,</span><br><span class="line"> birthday DATE,</span><br><span class="line"> profession VARCHAR(20) NOT NULL, -- 职称</span><br><span class="line"> department VARCHAR(20) NOT NULL -- 部门</span><br><span class="line">);</span><br><span class="line"></span><br><span class="line">-- 创建课程表</span><br><span class="line">CREATE TABLE course (</span><br><span class="line"> no VARCHAR(20) PRIMARY KEY,</span><br><span class="line"> name VARCHAR(20) NOT NULL,</span><br><span class="line"> t_no VARCHAR(20) NOT NULL, -- 教师编号</span><br><span class="line"> -- 表示该 tno 来自于 teacher 表中的 no 字段值</span><br><span class="line"> FOREIGN KEY(t_no) REFERENCES teacher(no)</span><br><span class="line">);</span><br><span class="line"></span><br><span class="line">-- 成绩表</span><br><span class="line">CREATE TABLE score (</span><br><span class="line"> s_no VARCHAR(20) NOT NULL, -- 学生编号</span><br><span class="line"> c_no VARCHAR(20) NOT NULL, -- 课程号</span><br><span class="line"> degree DECIMAL, -- 成绩</span><br><span class="line"> -- 表示该 s_no, c_no 分别来自于 student, course 表中的 no 字段值</span><br><span class="line"> FOREIGN KEY(s_no) REFERENCES student(no),</span><br><span class="line"> FOREIGN KEY(c_no) REFERENCES course(no),</span><br><span class="line"> -- 设置 s_no, c_no 为联合主键</span><br><span class="line"> PRIMARY KEY(s_no, c_no)</span><br><span class="line">);</span><br><span class="line"></span><br><span class="line">-- 查看所有表</span><br><span class="line">SHOW TABLES;</span><br><span class="line"></span><br><span class="line">-- 添加学生表数据</span><br><span class="line">INSERT INTO student VALUES('101', '曾华', '男', '1977-09-01', '95033');</span><br><span class="line">INSERT INTO student VALUES('102', '匡明', '男', '1975-10-02', '95031');</span><br><span class="line">INSERT INTO student VALUES('103', '王丽', '女', '1976-01-23', '95033');</span><br><span class="line">INSERT INTO student VALUES('104', '李军', '男', '1976-02-20', '95033');</span><br><span class="line">INSERT INTO student VALUES('105', '王芳', '女', '1975-02-10', '95031');</span><br><span class="line">INSERT INTO student VALUES('106', '陆军', '男', '1974-06-03', '95031');</span><br><span class="line">INSERT INTO student VALUES('107', '王尼玛', '男', '1976-02-20', '95033');</span><br><span class="line">INSERT INTO student VALUES('108', '张全蛋', '男', '1975-02-10', '95031');</span><br><span class="line">INSERT INTO student VALUES('109', '赵铁柱', '男', '1974-06-03', '95031');</span><br><span class="line"></span><br><span class="line">-- 添加教师表数据</span><br><span class="line">INSERT INTO teacher VALUES('804', '李诚', '男', '1958-12-02', '副教授', '计算机系');</span><br><span class="line">INSERT INTO teacher VALUES('856', '张旭', '男', '1969-03-12', '讲师', '电子工程系');</span><br><span class="line">INSERT INTO teacher VALUES('825', '王萍', '女', '1972-05-05', '助教', '计算机系');</span><br><span class="line">INSERT INTO teacher VALUES('831', '刘冰', '女', '1977-08-14', '助教', '电子工程系');</span><br><span class="line"></span><br><span class="line">-- 添加课程表数据</span><br><span class="line">INSERT INTO course VALUES('3-105', '计算机导论', '825');</span><br><span class="line">INSERT INTO course VALUES('3-245', '操作系统', '804');</span><br><span class="line">INSERT INTO course VALUES('6-166', '数字电路', '856');</span><br><span class="line">INSERT INTO course VALUES('9-888', '高等数学', '831');</span><br><span class="line"></span><br><span class="line">-- 添加添加成绩表数据</span><br><span class="line">INSERT INTO score VALUES('103', '3-105', '92');</span><br><span class="line">INSERT INTO score VALUES('103', '3-245', '86');</span><br><span class="line">INSERT INTO score VALUES('103', '6-166', '85');</span><br><span class="line">INSERT INTO score VALUES('105', '3-105', '88');</span><br><span class="line">INSERT INTO score VALUES('105', '3-245', '75');</span><br><span class="line">INSERT INTO score VALUES('105', '6-166', '79');</span><br><span class="line">INSERT INTO score VALUES('109', '3-105', '76');</span><br><span class="line">INSERT INTO score VALUES('109', '3-245', '68');</span><br><span class="line">INSERT INTO score VALUES('109', '6-166', '81');</span><br><span class="line"></span><br><span class="line">-- 查看表结构</span><br><span class="line">SELECT * FROM course;</span><br><span class="line">SELECT * FROM score;</span><br><span class="line">SELECT * FROM student;</span><br><span class="line">SELECT * FROM teacher;</span><br></pre></td></tr></table></figure><h3 id="1-到-10"><a href="#1-到-10" class="headerlink" title="1 到 10"></a>1 到 10</h3><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br></pre></td><td class="code"><pre><span class="line">-- 查询 student 表的所有行</span><br><span class="line">SELECT * FROM student;</span><br><span class="line"></span><br><span class="line">-- 查询 student 表中的 name、sex 和 class 字段的所有行</span><br><span class="line">SELECT name, sex, class FROM student;</span><br><span class="line"></span><br><span class="line">-- 查询 teacher 表中不重复的 department 列</span><br><span class="line">-- department: 去重查询</span><br><span class="line">SELECT DISTINCT department FROM teacher;</span><br><span class="line"></span><br><span class="line">-- 查询 score 表中成绩在60-80之间的所有行（区间查询和运算符查询）</span><br><span class="line">-- BETWEEN xx AND xx: 查询区间, AND 表示 "并且"</span><br><span class="line">SELECT * FROM score WHERE degree BETWEEN 60 AND 80;</span><br><span class="line">SELECT * FROM score WHERE degree > 60 AND degree < 80;</span><br><span class="line"></span><br><span class="line">-- 查询 score 表中成绩为 85, 86 或 88 的行</span><br><span class="line">-- IN: 查询规定中的多个值</span><br><span class="line">SELECT * FROM score WHERE degree IN (85, 86, 88);</span><br><span class="line"></span><br><span class="line">-- 查询 student 表中 '95031' 班或性别为 '女' 的所有行</span><br><span class="line">-- or: 表示或者关系</span><br><span class="line">SELECT * FROM student WHERE class = '95031' or sex = '女';</span><br><span class="line"></span><br><span class="line">-- 以 class 降序的方式查询 student 表的所有行</span><br><span class="line">-- DESC: 降序，从高到低</span><br><span class="line">-- ASC（默认）: 升序，从低到高</span><br><span class="line">SELECT * FROM student ORDER BY class DESC;</span><br><span class="line">SELECT * FROM student ORDER BY class ASC;</span><br><span class="line"></span><br><span class="line">-- 以 c_no 升序、degree 降序查询 score 表的所有行</span><br><span class="line">SELECT * FROM score ORDER BY c_no ASC, degree DESC;</span><br><span class="line"></span><br><span class="line">-- 查询 "95031" 班的学生人数</span><br><span class="line">-- COUNT: 统计</span><br><span class="line">SELECT COUNT(*) FROM student WHERE class = '95031';</span><br><span class="line"></span><br><span class="line">-- 查询 score 表中的最高分的学生学号和课程编号（子查询或排序查询）。</span><br><span class="line">-- (SELECT MAX(degree) FROM score): 子查询，算出最高分</span><br><span class="line">SELECT s_no, c_no FROM score WHERE degree = (SELECT MAX(degree) FROM score);</span><br><span class="line"></span><br><span class="line">-- 排序查询</span><br><span class="line">-- LIMIT r, n: 表示从第r行开始，查询n条数据</span><br><span class="line">SELECT s_no, c_no, degree FROM score ORDER BY degree DESC LIMIT 0, 1;</span><br></pre></td></tr></table></figure><h3 id="分组计算平均成绩"><a href="#分组计算平均成绩" class="headerlink" title="分组计算平均成绩"></a>分组计算平均成绩</h3><p><strong>查询每门课的平均成绩。</strong></p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line">-- AVG: 平均值</span><br><span class="line">SELECT AVG(degree) FROM score WHERE c_no = '3-105';</span><br><span class="line">SELECT AVG(degree) FROM score WHERE c_no = '3-245';</span><br><span class="line">SELECT AVG(degree) FROM score WHERE c_no = '6-166';</span><br><span class="line"></span><br><span class="line">-- GROUP BY: 分组查询</span><br><span class="line">SELECT c_no, AVG(degree) FROM score GROUP BY c_no;</span><br></pre></td></tr></table></figure><h3 id="分组条件与模糊查询"><a href="#分组条件与模糊查询" class="headerlink" title="分组条件与模糊查询"></a>分组条件与模糊查询</h3><p><strong>查询 <code>score</code> 表中至少有 2 名学生选修，并以 3 开头的课程的平均分数。</strong></p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line">SELECT * FROM score;</span><br><span class="line">-- c_no 课程编号</span><br><span class="line">+------+-------+--------+</span><br><span class="line">| s_no | c_no | degree |</span><br><span class="line">+------+-------+--------+</span><br><span class="line">| 103 | 3-105 | 92 |</span><br><span class="line">| 103 | 3-245 | 86 |</span><br><span class="line">| 103 | 6-166 | 85 |</span><br><span class="line">| 105 | 3-105 | 88 |</span><br><span class="line">| 105 | 3-245 | 75 |</span><br><span class="line">| 105 | 6-166 | 79 |</span><br><span class="line">| 109 | 3-105 | 76 |</span><br><span class="line">| 109 | 3-245 | 68 |</span><br><span class="line">| 109 | 6-166 | 81 |</span><br><span class="line">+------+-------+--------+</span><br></pre></td></tr></table></figure><p>分析表发现，至少有 2 名学生选修的课程是 <code>3-105</code> 、<code>3-245</code> 、<code>6-166</code> ，以 3 开头的课程是 <code>3-105</code> 、<code>3-245</code> 。也就是说，我们要查询所有 <code>3-105</code> 和 <code>3-245</code> 的 <code>degree</code> 平均分。</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br></pre></td><td class="code"><pre><span class="line">-- 首先把 c_no, AVG(degree) 通过分组查询出来</span><br><span class="line">SELECT c_no, AVG(degree) FROM score GROUP BY c_no</span><br><span class="line">+-------+-------------+</span><br><span class="line">| c_no | AVG(degree) |</span><br><span class="line">+-------+-------------+</span><br><span class="line">| 3-105 | 85.3333 |</span><br><span class="line">| 3-245 | 76.3333 |</span><br><span class="line">| 6-166 | 81.6667 |</span><br><span class="line">+-------+-------------+</span><br><span class="line"></span><br><span class="line">-- 再查询出至少有 2 名学生选修的课程</span><br><span class="line">-- HAVING: 表示持有</span><br><span class="line">HAVING COUNT(c_no) >= 2</span><br><span class="line"></span><br><span class="line">-- 并且是以 3 开头的课程</span><br><span class="line">-- LIKE 表示模糊查询，"%" 是一个通配符，匹配 "3" 后面的任意字符。</span><br><span class="line">AND c_no LIKE '3%';</span><br><span class="line"></span><br><span class="line">-- 把前面的SQL语句拼接起来，</span><br><span class="line">-- 后面加上一个 COUNT(*)，表示将每个分组的个数也查询出来。</span><br><span class="line">SELECT c_no, AVG(degree), COUNT(*) FROM score GROUP BY c_no</span><br><span class="line">HAVING COUNT(c_no) >= 2 AND c_no LIKE '3%';</span><br><span class="line">+-------+-------------+----------+</span><br><span class="line">| c_no | AVG(degree) | COUNT(*) |</span><br><span class="line">+-------+-------------+----------+</span><br><span class="line">| 3-105 | 85.3333 | 3 |</span><br><span class="line">| 3-245 | 76.3333 | 3 |</span><br><span class="line">+-------+-------------+----------+</span><br></pre></td></tr></table></figure><h3 id="多表查询-1"><a href="#多表查询-1" class="headerlink" title="多表查询 - 1"></a>多表查询 - 1</h3><p><strong>查询所有学生的 <code>name</code>，以及该学生在 <code>score</code> 表中对应的 <code>c_no</code> 和 <code>degree</code> 。</strong></p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br></pre></td><td class="code"><pre><span class="line">SELECT no, name FROM student;</span><br><span class="line">+-----+-----------+</span><br><span class="line">| no | name |</span><br><span class="line">+-----+-----------+</span><br><span class="line">| 101 | 曾华 |</span><br><span class="line">| 102 | 匡明 |</span><br><span class="line">| 103 | 王丽 |</span><br><span class="line">| 104 | 李军 |</span><br><span class="line">| 105 | 王芳 |</span><br><span class="line">| 106 | 陆军 |</span><br><span class="line">| 107 | 王尼玛 |</span><br><span class="line">| 108 | 张全蛋 |</span><br><span class="line">| 109 | 赵铁柱 |</span><br><span class="line">+-----+-----------+</span><br><span class="line"></span><br><span class="line">SELECT s_no, c_no, degree FROM score;</span><br><span class="line">+------+-------+--------+</span><br><span class="line">| s_no | c_no | degree |</span><br><span class="line">+------+-------+--------+</span><br><span class="line">| 103 | 3-105 | 92 |</span><br><span class="line">| 103 | 3-245 | 86 |</span><br><span class="line">| 103 | 6-166 | 85 |</span><br><span class="line">| 105 | 3-105 | 88 |</span><br><span class="line">| 105 | 3-245 | 75 |</span><br><span class="line">| 105 | 6-166 | 79 |</span><br><span class="line">| 109 | 3-105 | 76 |</span><br><span class="line">| 109 | 3-245 | 68 |</span><br><span class="line">| 109 | 6-166 | 81 |</span><br><span class="line">+------+-------+--------+</span><br></pre></td></tr></table></figure><p>通过分析可以发现，只要把 <code>score</code> 表中的 <code>s_no</code> 字段值替换成 <code>student</code> 表中对应的 <code>name</code> 字段值就可以了，如何做呢？</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br></pre></td><td class="code"><pre><span class="line">-- FROM...: 表示从 student, score 表中查询</span><br><span class="line">-- WHERE 的条件表示为，只有在 student.no 和 score.s_no 相等时才显示出来。</span><br><span class="line">SELECT name, c_no, degree FROM student, score</span><br><span class="line">WHERE student.no = score.s_no;</span><br><span class="line">+-----------+-------+--------+</span><br><span class="line">| name | c_no | degree |</span><br><span class="line">+-----------+-------+--------+</span><br><span class="line">| 王丽 | 3-105 | 92 |</span><br><span class="line">| 王丽 | 3-245 | 86 |</span><br><span class="line">| 王丽 | 6-166 | 85 |</span><br><span class="line">| 王芳 | 3-105 | 88 |</span><br><span class="line">| 王芳 | 3-245 | 75 |</span><br><span class="line">| 王芳 | 6-166 | 79 |</span><br><span class="line">| 赵铁柱 | 3-105 | 76 |</span><br><span class="line">| 赵铁柱 | 3-245 | 68 |</span><br><span class="line">| 赵铁柱 | 6-166 | 81 |</span><br><span class="line">+-----------+-------+--------+</span><br></pre></td></tr></table></figure><h3 id="多表查询-2"><a href="#多表查询-2" class="headerlink" title="多表查询 - 2"></a>多表查询 - 2</h3><p><strong>查询所有学生的 <code>no</code> 、课程名称 ( <code>course</code> 表中的 <code>name</code> ) 和成绩 ( <code>score</code> 表中的 <code>degree</code> ) 列。</strong></p><p>只有 <code>score</code> 关联学生的 <code>no</code> ，因此只要查询 <code>score</code> 表，就能找出所有和学生相关的 <code>no</code> 和 <code>degree</code> ：</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line">SELECT s_no, c_no, degree FROM score;</span><br><span class="line">+------+-------+--------+</span><br><span class="line">| s_no | c_no | degree |</span><br><span class="line">+------+-------+--------+</span><br><span class="line">| 103 | 3-105 | 92 |</span><br><span class="line">| 103 | 3-245 | 86 |</span><br><span class="line">| 103 | 6-166 | 85 |</span><br><span class="line">| 105 | 3-105 | 88 |</span><br><span class="line">| 105 | 3-245 | 75 |</span><br><span class="line">| 105 | 6-166 | 79 |</span><br><span class="line">| 109 | 3-105 | 76 |</span><br><span class="line">| 109 | 3-245 | 68 |</span><br><span class="line">| 109 | 6-166 | 81 |</span><br><span class="line">+------+-------+--------+</span><br></pre></td></tr></table></figure><p>然后查询 <code>course</code> 表：</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line">+-------+-----------------+</span><br><span class="line">| no | name |</span><br><span class="line">+-------+-----------------+</span><br><span class="line">| 3-105 | 计算机导论 |</span><br><span class="line">| 3-245 | 操作系统 |</span><br><span class="line">| 6-166 | 数字电路 |</span><br><span class="line">| 9-888 | 高等数学 |</span><br><span class="line">+-------+-----------------+</span><br></pre></td></tr></table></figure><p>只要把 <code>score</code> 表中的 <code>c_no</code> 替换成 <code>course</code> 表中对应的 <code>name</code> 字段值就可以了。</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br></pre></td><td class="code"><pre><span class="line">-- 增加一个查询字段 name，分别从 score、course 这两个表中查询。</span><br><span class="line">-- as 表示取一个该字段的别名。</span><br><span class="line">SELECT s_no, name as c_name, degree FROM score, course</span><br><span class="line">WHERE score.c_no = course.no;</span><br><span class="line">+------+-----------------+--------+</span><br><span class="line">| s_no | c_name | degree |</span><br><span class="line">+------+-----------------+--------+</span><br><span class="line">| 103 | 计算机导论 | 92 |</span><br><span class="line">| 105 | 计算机导论 | 88 |</span><br><span class="line">| 109 | 计算机导论 | 76 |</span><br><span class="line">| 103 | 操作系统 | 86 |</span><br><span class="line">| 105 | 操作系统 | 75 |</span><br><span class="line">| 109 | 操作系统 | 68 |</span><br><span class="line">| 103 | 数字电路 | 85 |</span><br><span class="line">| 105 | 数字电路 | 79 |</span><br><span class="line">| 109 | 数字电路 | 81 |</span><br><span class="line">+------+-----------------+--------+</span><br></pre></td></tr></table></figure><h3 id="三表关联查询"><a href="#三表关联查询" class="headerlink" title="三表关联查询"></a>三表关联查询</h3><p><strong>查询所有学生的 <code>name</code> 、课程名 ( <code>course</code> 表中的 <code>name</code> ) 和 <code>degree</code> 。</strong></p><p>只有 <code>score</code> 表中关联学生的学号和课堂号，我们只要围绕着 <code>score</code> 这张表查询就好了。</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line">SELECT * FROM score;</span><br><span class="line">+------+-------+--------+</span><br><span class="line">| s_no | c_no | degree |</span><br><span class="line">+------+-------+--------+</span><br><span class="line">| 103 | 3-105 | 92 |</span><br><span class="line">| 103 | 3-245 | 86 |</span><br><span class="line">| 103 | 6-166 | 85 |</span><br><span class="line">| 105 | 3-105 | 88 |</span><br><span class="line">| 105 | 3-245 | 75 |</span><br><span class="line">| 105 | 6-166 | 79 |</span><br><span class="line">| 109 | 3-105 | 76 |</span><br><span class="line">| 109 | 3-245 | 68 |</span><br><span class="line">| 109 | 6-166 | 81 |</span><br><span class="line">+------+-------+--------+</span><br></pre></td></tr></table></figure><p>只要把 <code>s_no</code> 和 <code>c_no</code> 替换成 <code>student</code> 和 <code>srouse</code> 表中对应的 <code>name</code> 字段值就好了。</p><p>首先把 <code>s_no</code> 替换成 <code>student</code> 表中的 <code>name</code> 字段：</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line">SELECT name, c_no, degree FROM student, score WHERE student.no = score.s_no;</span><br><span class="line">+-----------+-------+--------+</span><br><span class="line">| name | c_no | degree |</span><br><span class="line">+-----------+-------+--------+</span><br><span class="line">| 王丽 | 3-105 | 92 |</span><br><span class="line">| 王丽 | 3-245 | 86 |</span><br><span class="line">| 王丽 | 6-166 | 85 |</span><br><span class="line">| 王芳 | 3-105 | 88 |</span><br><span class="line">| 王芳 | 3-245 | 75 |</span><br><span class="line">| 王芳 | 6-166 | 79 |</span><br><span class="line">| 赵铁柱 | 3-105 | 76 |</span><br><span class="line">| 赵铁柱 | 3-245 | 68 |</span><br><span class="line">| 赵铁柱 | 6-166 | 81 |</span><br><span class="line">+-----------+-------+--------+</span><br></pre></td></tr></table></figure><p>再把 <code>c_no</code> 替换成 <code>course</code> 表中的 <code>name</code> 字段：</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br></pre></td><td class="code"><pre><span class="line">-- 课程表</span><br><span class="line">SELECT no, name FROM course;</span><br><span class="line">+-------+-----------------+</span><br><span class="line">| no | name |</span><br><span class="line">+-------+-----------------+</span><br><span class="line">| 3-105 | 计算机导论 |</span><br><span class="line">| 3-245 | 操作系统 |</span><br><span class="line">| 6-166 | 数字电路 |</span><br><span class="line">| 9-888 | 高等数学 |</span><br><span class="line">+-------+-----------------+</span><br><span class="line"></span><br><span class="line">-- 由于字段名存在重复，使用 "表名.字段名 as 别名" 代替。</span><br><span class="line">SELECT student.name as s_name, course.name as c_name, degree</span><br><span class="line">FROM student, score, course</span><br><span class="line">WHERE student.NO = score.s_no</span><br><span class="line">AND score.c_no = course.no;</span><br></pre></td></tr></table></figure><h3 id="子查询加分组求平均分"><a href="#子查询加分组求平均分" class="headerlink" title="子查询加分组求平均分"></a>子查询加分组求平均分</h3><p><strong>查询 <code>95031</code> 班学生每门课程的平均成绩。</strong></p><p>在 <code>score</code> 表中根据 <code>student</code> 表的学生编号筛选出学生的课堂号和成绩：</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br></pre></td><td class="code"><pre><span class="line">-- IN (..): 将筛选出的学生号当做 s_no 的条件查询</span><br><span class="line">SELECT s_no, c_no, degree FROM score</span><br><span class="line">WHERE s_no IN (SELECT no FROM student WHERE class = '95031');</span><br><span class="line">+------+-------+--------+</span><br><span class="line">| s_no | c_no | degree |</span><br><span class="line">+------+-------+--------+</span><br><span class="line">| 105 | 3-105 | 88 |</span><br><span class="line">| 105 | 3-245 | 75 |</span><br><span class="line">| 105 | 6-166 | 79 |</span><br><span class="line">| 109 | 3-105 | 76 |</span><br><span class="line">| 109 | 3-245 | 68 |</span><br><span class="line">| 109 | 6-166 | 81 |</span><br><span class="line">+------+-------+--------+</span><br></pre></td></tr></table></figure><p>这时只要将 <code>c_no</code> 分组一下就能得出 <code>95031</code> 班学生每门课的平均成绩：</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line">SELECT c_no, AVG(degree) FROM score</span><br><span class="line">WHERE s_no IN (SELECT no FROM student WHERE class = '95031')</span><br><span class="line">GROUP BY c_no;</span><br><span class="line">+-------+-------------+</span><br><span class="line">| c_no | AVG(degree) |</span><br><span class="line">+-------+-------------+</span><br><span class="line">| 3-105 | 82.0000 |</span><br><span class="line">| 3-245 | 71.5000 |</span><br><span class="line">| 6-166 | 80.0000 |</span><br><span class="line">+-------+-------------+</span><br></pre></td></tr></table></figure><h3 id="子查询-1"><a href="#子查询-1" class="headerlink" title="子查询 - 1"></a>子查询 - 1</h3><p><strong>查询在 <code>3-105</code> 课程中，所有成绩高于 <code>109</code> 号同学的记录。</strong></p><p>首先筛选出课堂号为 <code>3-105</code> ，在找出所有成绩高于 <code>109</code> 号同学的的行。</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">SELECT * FROM score</span><br><span class="line">WHERE c_no = '3-105'</span><br><span class="line">AND degree > (SELECT degree FROM score WHERE s_no = '109' AND c_no = '3-105');</span><br></pre></td></tr></table></figure><h3 id="子查询-2"><a href="#子查询-2" class="headerlink" title="子查询 - 2"></a>子查询 - 2</h3><p><strong>查询所有成绩高于 <code>109</code> 号同学的 <code>3-105</code> 课程成绩记录。</strong></p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">-- 不限制课程号，只要成绩大于109号同学的3-105课程成绩就可以。</span><br><span class="line">SELECT * FROM score</span><br><span class="line">WHERE degree > (SELECT degree FROM score WHERE s_no = '109' AND c_no = '3-105');</span><br></pre></td></tr></table></figure><h3 id="YEAR-函数与带-IN-关键字查询"><a href="#YEAR-函数与带-IN-关键字查询" class="headerlink" title="YEAR 函数与带 IN 关键字查询"></a>YEAR 函数与带 IN 关键字查询</h3><p><strong>查询所有和 <code>101</code> 、<code>108</code> 号学生同年出生的 <code>no</code> 、<code>name</code> 、<code>birthday</code> 列。</strong></p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">-- YEAR(..): 取出日期中的年份</span><br><span class="line">SELECT no, name, birthday FROM student</span><br><span class="line">WHERE YEAR(birthday) IN (SELECT YEAR(birthday) FROM student WHERE no IN (101, 108));</span><br></pre></td></tr></table></figure><h3 id="多层嵌套子查询"><a href="#多层嵌套子查询" class="headerlink" title="多层嵌套子查询"></a>多层嵌套子查询</h3><p><strong>查询 <code>'张旭'</code> 教师任课的学生成绩表。</strong></p><p>首先找到教师编号：</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">SELECT NO FROM teacher WHERE NAME = '张旭'</span><br></pre></td></tr></table></figure><p>通过 <code>sourse</code> 表找到该教师课程号：</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">SELECT NO FROM course WHERE t_no = ( SELECT NO FROM teacher WHERE NAME = '张旭' );</span><br></pre></td></tr></table></figure><p>通过筛选出的课程号查询成绩表：</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">SELECT * FROM score WHERE c_no = (</span><br><span class="line"> SELECT no FROM course WHERE t_no = (</span><br><span class="line"> SELECT no FROM teacher WHERE NAME = '张旭'</span><br><span class="line"> )</span><br><span class="line">);</span><br></pre></td></tr></table></figure><h3 id="多表查询"><a href="#多表查询" class="headerlink" title="多表查询"></a>多表查询</h3><p><strong>查询某选修课程多于5个同学的教师姓名。</strong></p><p>首先在 <code>teacher</code> 表中，根据 <code>no</code> 字段来判断该教师的同一门课程是否有至少5名学员选修：</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line">-- 查询 teacher 表</span><br><span class="line">SELECT no, name FROM teacher;</span><br><span class="line">+-----+--------+</span><br><span class="line">| no | name |</span><br><span class="line">+-----+--------+</span><br><span class="line">| 804 | 李诚 |</span><br><span class="line">| 825 | 王萍 |</span><br><span class="line">| 831 | 刘冰 |</span><br><span class="line">| 856 | 张旭 |</span><br><span class="line">+-----+--------+</span><br><span class="line"></span><br><span class="line">SELECT name FROM teacher WHERE no IN (</span><br><span class="line"> -- 在这里找到对应的条件</span><br><span class="line">);</span><br></pre></td></tr></table></figure><p>查看和教师编号有有关的表的信息：</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line">SELECT * FROM course;</span><br><span class="line">-- t_no: 教师编号</span><br><span class="line">+-------+-----------------+------+</span><br><span class="line">| no | name | t_no |</span><br><span class="line">+-------+-----------------+------+</span><br><span class="line">| 3-105 | 计算机导论 | 825 |</span><br><span class="line">| 3-245 | 操作系统 | 804 |</span><br><span class="line">| 6-166 | 数字电路 | 856 |</span><br><span class="line">| 9-888 | 高等数学 | 831 |</span><br><span class="line">+-------+-----------------+------+</span><br></pre></td></tr></table></figure><p>我们已经找到和教师编号有关的字段就在 <code>course</code> 表中，但是还无法知道哪门课程至少有5名学生选修，所以还需要根据 <code>score</code> 表来查询：</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br></pre></td><td class="code"><pre><span class="line">-- 在此之前向 score 插入一些数据，以便丰富查询条件。</span><br><span class="line">INSERT INTO score VALUES ('101', '3-105', '90');</span><br><span class="line">INSERT INTO score VALUES ('102', '3-105', '91');</span><br><span class="line">INSERT INTO score VALUES ('104', '3-105', '89');</span><br><span class="line"></span><br><span class="line">-- 查询 score 表</span><br><span class="line">SELECT * FROM score;</span><br><span class="line">+------+-------+--------+</span><br><span class="line">| s_no | c_no | degree |</span><br><span class="line">+------+-------+--------+</span><br><span class="line">| 101 | 3-105 | 90 |</span><br><span class="line">| 102 | 3-105 | 91 |</span><br><span class="line">| 103 | 3-105 | 92 |</span><br><span class="line">| 103 | 3-245 | 86 |</span><br><span class="line">| 103 | 6-166 | 85 |</span><br><span class="line">| 104 | 3-105 | 89 |</span><br><span class="line">| 105 | 3-105 | 88 |</span><br><span class="line">| 105 | 3-245 | 75 |</span><br><span class="line">| 105 | 6-166 | 79 |</span><br><span class="line">| 109 | 3-105 | 76 |</span><br><span class="line">| 109 | 3-245 | 68 |</span><br><span class="line">| 109 | 6-166 | 81 |</span><br><span class="line">+------+-------+--------+</span><br><span class="line"></span><br><span class="line">-- 在 score 表中将 c_no 作为分组，并且限制 c_no 持有至少 5 条数据。</span><br><span class="line">SELECT c_no FROM score GROUP BY c_no HAVING COUNT(*) > 5;</span><br><span class="line">+-------+</span><br><span class="line">| c_no |</span><br><span class="line">+-------+</span><br><span class="line">| 3-105 |</span><br><span class="line">+-------+</span><br></pre></td></tr></table></figure><p>根据筛选出来的课程号，找出在某课程中，拥有至少5名学员的教师编号：</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line">SELECT t_no FROM course WHERE no IN (</span><br><span class="line"> SELECT c_no FROM score GROUP BY c_no HAVING COUNT(*) > 5</span><br><span class="line">);</span><br><span class="line">+------+</span><br><span class="line">| t_no |</span><br><span class="line">+------+</span><br><span class="line">| 825 |</span><br><span class="line">+------+</span><br></pre></td></tr></table></figure><p>在 <code>teacher</code> 表中，根据筛选出来的教师编号找到教师姓名：</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line">SELECT name FROM teacher WHERE no IN (</span><br><span class="line"> -- 最终条件</span><br><span class="line"> SELECT t_no FROM course WHERE no IN (</span><br><span class="line"> SELECT c_no FROM score GROUP BY c_no HAVING COUNT(*) > 5</span><br><span class="line"> )</span><br><span class="line">);</span><br></pre></td></tr></table></figure><h3 id="子查询-3"><a href="#子查询-3" class="headerlink" title="子查询 - 3"></a>子查询 - 3</h3><p><strong>查询 “计算机系” 课程的成绩表。</strong></p><p>思路是，先找出 <code>course</code> 表中所有 <code>计算机系</code> 课程的编号，然后根据这个编号查询 <code>score</code> 表。</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br></pre></td><td class="code"><pre><span class="line">-- 通过 teacher 表查询所有 `计算机系` 的教师编号</span><br><span class="line">SELECT no, name, department FROM teacher WHERE department = '计算机系'</span><br><span class="line">+-----+--------+--------------+</span><br><span class="line">| no | name | department |</span><br><span class="line">+-----+--------+--------------+</span><br><span class="line">| 804 | 李诚 | 计算机系 |</span><br><span class="line">| 825 | 王萍 | 计算机系 |</span><br><span class="line">+-----+--------+--------------+</span><br><span class="line"></span><br><span class="line">-- 通过 course 表查询该教师的课程编号</span><br><span class="line">SELECT no FROM course WHERE t_no IN (</span><br><span class="line"> SELECT no FROM teacher WHERE department = '计算机系'</span><br><span class="line">);</span><br><span class="line">+-------+</span><br><span class="line">| no |</span><br><span class="line">+-------+</span><br><span class="line">| 3-245 |</span><br><span class="line">| 3-105 |</span><br><span class="line">+-------+</span><br><span class="line"></span><br><span class="line">-- 根据筛选出来的课程号查询成绩表</span><br><span class="line">SELECT * FROM score WHERE c_no IN (</span><br><span class="line"> SELECT no FROM course WHERE t_no IN (</span><br><span class="line"> SELECT no FROM teacher WHERE department = '计算机系'</span><br><span class="line"> )</span><br><span class="line">);</span><br><span class="line">+------+-------+--------+</span><br><span class="line">| s_no | c_no | degree |</span><br><span class="line">+------+-------+--------+</span><br><span class="line">| 103 | 3-245 | 86 |</span><br><span class="line">| 105 | 3-245 | 75 |</span><br><span class="line">| 109 | 3-245 | 68 |</span><br><span class="line">| 101 | 3-105 | 90 |</span><br><span class="line">| 102 | 3-105 | 91 |</span><br><span class="line">| 103 | 3-105 | 92 |</span><br><span class="line">| 104 | 3-105 | 89 |</span><br><span class="line">| 105 | 3-105 | 88 |</span><br><span class="line">| 109 | 3-105 | 76 |</span><br><span class="line">+------+-------+--------+</span><br></pre></td></tr></table></figure><h3 id="UNION-和-NOTIN-的使用"><a href="#UNION-和-NOTIN-的使用" class="headerlink" title="UNION 和 NOTIN 的使用"></a>UNION 和 NOTIN 的使用</h3><p><strong>查询 <code>计算机系</code> 与 <code>电子工程系</code> 中的不同职称的教师。</strong></p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line">-- NOT: 代表逻辑非</span><br><span class="line">SELECT * FROM teacher WHERE department = '计算机系' AND profession NOT IN (</span><br><span class="line"> SELECT profession FROM teacher WHERE department = '电子工程系'</span><br><span class="line">)</span><br><span class="line">-- 合并两个集</span><br><span class="line">UNION</span><br><span class="line">SELECT * FROM teacher WHERE department = '电子工程系' AND profession NOT IN (</span><br><span class="line"> SELECT profession FROM teacher WHERE department = '计算机系'</span><br><span class="line">);</span><br></pre></td></tr></table></figure><h3 id="ANY-表示至少一个-DESC-降序"><a href="#ANY-表示至少一个-DESC-降序" class="headerlink" title="ANY 表示至少一个 - DESC ( 降序 )"></a>ANY 表示至少一个 - DESC ( 降序 )</h3><!-- markdownlint-disable MD033 --><p><strong>查询课程 <code>3-105</code> 且成绩 <u>至少</u> 高于 <code>3-245</code> 的 <code>score</code> 表。</strong></p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br></pre></td><td class="code"><pre><span class="line">SELECT * FROM score WHERE c_no = '3-105';</span><br><span class="line">+------+-------+--------+</span><br><span class="line">| s_no | c_no | degree |</span><br><span class="line">+------+-------+--------+</span><br><span class="line">| 101 | 3-105 | 90 |</span><br><span class="line">| 102 | 3-105 | 91 |</span><br><span class="line">| 103 | 3-105 | 92 |</span><br><span class="line">| 104 | 3-105 | 89 |</span><br><span class="line">| 105 | 3-105 | 88 |</span><br><span class="line">| 109 | 3-105 | 76 |</span><br><span class="line">+------+-------+--------+</span><br><span class="line"></span><br><span class="line">SELECT * FROM score WHERE c_no = '3-245';</span><br><span class="line">+------+-------+--------+</span><br><span class="line">| s_no | c_no | degree |</span><br><span class="line">+------+-------+--------+</span><br><span class="line">| 103 | 3-245 | 86 |</span><br><span class="line">| 105 | 3-245 | 75 |</span><br><span class="line">| 109 | 3-245 | 68 |</span><br><span class="line">+------+-------+--------+</span><br><span class="line"></span><br><span class="line">-- ANY: 符合SQL语句中的任意条件。</span><br><span class="line">-- 也就是说，在 3-105 成绩中，只要有一个大于从 3-245 筛选出来的任意行就符合条件，</span><br><span class="line">-- 最后根据降序查询结果。</span><br><span class="line">SELECT * FROM score WHERE c_no = '3-105' AND degree > ANY(</span><br><span class="line"> SELECT degree FROM score WHERE c_no = '3-245'</span><br><span class="line">) ORDER BY degree DESC;</span><br><span class="line">+------+-------+--------+</span><br><span class="line">| s_no | c_no | degree |</span><br><span class="line">+------+-------+--------+</span><br><span class="line">| 103 | 3-105 | 92 |</span><br><span class="line">| 102 | 3-105 | 91 |</span><br><span class="line">| 101 | 3-105 | 90 |</span><br><span class="line">| 104 | 3-105 | 89 |</span><br><span class="line">| 105 | 3-105 | 88 |</span><br><span class="line">| 109 | 3-105 | 76 |</span><br><span class="line">+------+-------+--------+</span><br></pre></td></tr></table></figure><h3 id="表示所有的-ALL"><a href="#表示所有的-ALL" class="headerlink" title="表示所有的 ALL"></a>表示所有的 ALL</h3><p><strong>查询课程 <code>3-105</code> 且成绩高于 <code>3-245</code> 的 <code>score</code> 表。</strong></p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line">-- 只需对上一道题稍作修改。</span><br><span class="line">-- ALL: 符合SQL语句中的所有条件。</span><br><span class="line">-- 也就是说，在 3-105 每一行成绩中，都要大于从 3-245 筛选出来全部行才算符合条件。</span><br><span class="line">SELECT * FROM score WHERE c_no = '3-105' AND degree > ALL(</span><br><span class="line"> SELECT degree FROM score WHERE c_no = '3-245'</span><br><span class="line">);</span><br><span class="line">+------+-------+--------+</span><br><span class="line">| s_no | c_no | degree |</span><br><span class="line">+------+-------+--------+</span><br><span class="line">| 101 | 3-105 | 90 |</span><br><span class="line">| 102 | 3-105 | 91 |</span><br><span class="line">| 103 | 3-105 | 92 |</span><br><span class="line">| 104 | 3-105 | 89 |</span><br><span class="line">| 105 | 3-105 | 88 |</span><br><span class="line">+------+-------+--------+</span><br></pre></td></tr></table></figure><h3 id="复制表的数据作为条件查询"><a href="#复制表的数据作为条件查询" class="headerlink" title="复制表的数据作为条件查询"></a>复制表的数据作为条件查询</h3><p><strong>查询某课程成绩比该课程平均成绩低的 <code>score</code> 表。</strong></p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br></pre></td><td class="code"><pre><span class="line">-- 查询平均分</span><br><span class="line">SELECT c_no, AVG(degree) FROM score GROUP BY c_no;</span><br><span class="line">+-------+-------------+</span><br><span class="line">| c_no | AVG(degree) |</span><br><span class="line">+-------+-------------+</span><br><span class="line">| 3-105 | 87.6667 |</span><br><span class="line">| 3-245 | 76.3333 |</span><br><span class="line">| 6-166 | 81.6667 |</span><br><span class="line">+-------+-------------+</span><br><span class="line"></span><br><span class="line">-- 查询 score 表</span><br><span class="line">SELECT degree FROM score;</span><br><span class="line">+--------+</span><br><span class="line">| degree |</span><br><span class="line">+--------+</span><br><span class="line">| 90 |</span><br><span class="line">| 91 |</span><br><span class="line">| 92 |</span><br><span class="line">| 86 |</span><br><span class="line">| 85 |</span><br><span class="line">| 89 |</span><br><span class="line">| 88 |</span><br><span class="line">| 75 |</span><br><span class="line">| 79 |</span><br><span class="line">| 76 |</span><br><span class="line">| 68 |</span><br><span class="line">| 81 |</span><br><span class="line">+--------+</span><br><span class="line"></span><br><span class="line">-- 将表 b 作用于表 a 中查询数据</span><br><span class="line">-- score a (b): 将表声明为 a (b)，</span><br><span class="line">-- 如此就能用 a.c_no = b.c_no 作为条件执行查询了。</span><br><span class="line">SELECT * FROM score a WHERE degree < (</span><br><span class="line"> (SELECT AVG(degree) FROM score b WHERE a.c_no = b.c_no)</span><br><span class="line">);</span><br><span class="line">+------+-------+--------+</span><br><span class="line">| s_no | c_no | degree |</span><br><span class="line">+------+-------+--------+</span><br><span class="line">| 105 | 3-245 | 75 |</span><br><span class="line">| 105 | 6-166 | 79 |</span><br><span class="line">| 109 | 3-105 | 76 |</span><br><span class="line">| 109 | 3-245 | 68 |</span><br><span class="line">| 109 | 6-166 | 81 |</span><br><span class="line">+------+-------+--------+</span><br></pre></td></tr></table></figure><h3 id="子查询-4"><a href="#子查询-4" class="headerlink" title="子查询 - 4"></a>子查询 - 4</h3><p><strong>查询所有任课 ( 在 <code>course</code> 表里有课程 ) 教师的 <code>name</code> 和 <code>department</code></strong> 。</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line">SELECT name, department FROM teacher WHERE no IN (SELECT t_no FROM course);</span><br><span class="line">+--------+-----------------+</span><br><span class="line">| name | department |</span><br><span class="line">+--------+-----------------+</span><br><span class="line">| 李诚 | 计算机系 |</span><br><span class="line">| 王萍 | 计算机系 |</span><br><span class="line">| 刘冰 | 电子工程系 |</span><br><span class="line">| 张旭 | 电子工程系 |</span><br><span class="line">+--------+-----------------+</span><br></pre></td></tr></table></figure><h3 id="条件加组筛选"><a href="#条件加组筛选" class="headerlink" title="条件加组筛选"></a>条件加组筛选</h3><p><strong>查询 <code>student</code> 表中至少有 2 名男生的 <code>class</code> 。</strong></p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br></pre></td><td class="code"><pre><span class="line">-- 查看学生表信息</span><br><span class="line">SELECT * FROM student;</span><br><span class="line">+-----+-----------+-----+------------+-------+</span><br><span class="line">| no | name | sex | birthday | class |</span><br><span class="line">+-----+-----------+-----+------------+-------+</span><br><span class="line">| 101 | 曾华 | 男 | 1977-09-01 | 95033 |</span><br><span class="line">| 102 | 匡明 | 男 | 1975-10-02 | 95031 |</span><br><span class="line">| 103 | 王丽 | 女 | 1976-01-23 | 95033 |</span><br><span class="line">| 104 | 李军 | 男 | 1976-02-20 | 95033 |</span><br><span class="line">| 105 | 王芳 | 女 | 1975-02-10 | 95031 |</span><br><span class="line">| 106 | 陆军 | 男 | 1974-06-03 | 95031 |</span><br><span class="line">| 107 | 王尼玛 | 男 | 1976-02-20 | 95033 |</span><br><span class="line">| 108 | 张全蛋 | 男 | 1975-02-10 | 95031 |</span><br><span class="line">| 109 | 赵铁柱 | 男 | 1974-06-03 | 95031 |</span><br><span class="line">| 110 | 张飞 | 男 | 1974-06-03 | 95038 |</span><br><span class="line">+-----+-----------+-----+------------+-------+</span><br><span class="line"></span><br><span class="line">-- 只查询性别为男，然后按 class 分组，并限制 class 行大于 1。</span><br><span class="line">SELECT class FROM student WHERE sex = '男' GROUP BY class HAVING COUNT(*) > 1;</span><br><span class="line">+-------+</span><br><span class="line">| class |</span><br><span class="line">+-------+</span><br><span class="line">| 95033 |</span><br><span class="line">| 95031 |</span><br><span class="line">+-------+</span><br></pre></td></tr></table></figure><h3 id="NOTLIKE-模糊查询取反"><a href="#NOTLIKE-模糊查询取反" class="headerlink" title="NOTLIKE 模糊查询取反"></a>NOTLIKE 模糊查询取反</h3><p><strong>查询 <code>student</code> 表中不姓 “王” 的同学记录。</strong></p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line">-- NOT: 取反</span><br><span class="line">-- LIKE: 模糊查询</span><br><span class="line">mysql> SELECT * FROM student WHERE name NOT LIKE '王%';</span><br><span class="line">+-----+-----------+-----+------------+-------+</span><br><span class="line">| no | name | sex | birthday | class |</span><br><span class="line">+-----+-----------+-----+------------+-------+</span><br><span class="line">| 101 | 曾华 | 男 | 1977-09-01 | 95033 |</span><br><span class="line">| 102 | 匡明 | 男 | 1975-10-02 | 95031 |</span><br><span class="line">| 104 | 李军 | 男 | 1976-02-20 | 95033 |</span><br><span class="line">| 106 | 陆军 | 男 | 1974-06-03 | 95031 |</span><br><span class="line">| 108 | 张全蛋 | 男 | 1975-02-10 | 95031 |</span><br><span class="line">| 109 | 赵铁柱 | 男 | 1974-06-03 | 95031 |</span><br><span class="line">| 110 | 张飞 | 男 | 1974-06-03 | 95038 |</span><br><span class="line">+-----+-----------+-----+------------+-------+</span><br></pre></td></tr></table></figure><h3 id="YEAR-与-NOW-函数"><a href="#YEAR-与-NOW-函数" class="headerlink" title="YEAR 与 NOW 函数"></a>YEAR 与 NOW 函数</h3><p><strong>查询 <code>student</code> 表中每个学生的姓名和年龄。</strong></p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br></pre></td><td class="code"><pre><span class="line">-- 使用函数 YEAR(NOW()) 计算出当前年份，减去出生年份后得出年龄。</span><br><span class="line">SELECT name, YEAR(NOW()) - YEAR(birthday) as age FROM student;</span><br><span class="line">+-----------+------+</span><br><span class="line">| name | age |</span><br><span class="line">+-----------+------+</span><br><span class="line">| 曾华 | 42 |</span><br><span class="line">| 匡明 | 44 |</span><br><span class="line">| 王丽 | 43 |</span><br><span class="line">| 李军 | 43 |</span><br><span class="line">| 王芳 | 44 |</span><br><span class="line">| 陆军 | 45 |</span><br><span class="line">| 王尼玛 | 43 |</span><br><span class="line">| 张全蛋 | 44 |</span><br><span class="line">| 赵铁柱 | 45 |</span><br><span class="line">| 张飞 | 45 |</span><br><span class="line">+-----------+------+</span><br></pre></td></tr></table></figure><h3 id="MAX-与-MIN-函数"><a href="#MAX-与-MIN-函数" class="headerlink" title="MAX 与 MIN 函数"></a>MAX 与 MIN 函数</h3><p><strong>查询 <code>student</code> 表中最大和最小的 <code>birthday</code> 值。</strong></p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line">SELECT MAX(birthday), MIN(birthday) FROM student;</span><br><span class="line">+---------------+---------------+</span><br><span class="line">| MAX(birthday) | MIN(birthday) |</span><br><span class="line">+---------------+---------------+</span><br><span class="line">| 1977-09-01 | 1974-06-03 |</span><br><span class="line">+---------------+---------------+</span><br></pre></td></tr></table></figure><h3 id="多段排序"><a href="#多段排序" class="headerlink" title="多段排序"></a>多段排序</h3><p><strong>以 <code>class</code> 和 <code>birthday</code> 从大到小的顺序查询 <code>student</code> 表。</strong></p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line">SELECT * FROM student ORDER BY class DESC, birthday;</span><br><span class="line">+-----+-----------+-----+------------+-------+</span><br><span class="line">| no | name | sex | birthday | class |</span><br><span class="line">+-----+-----------+-----+------------+-------+</span><br><span class="line">| 110 | 张飞 | 男 | 1974-06-03 | 95038 |</span><br><span class="line">| 103 | 王丽 | 女 | 1976-01-23 | 95033 |</span><br><span class="line">| 104 | 李军 | 男 | 1976-02-20 | 95033 |</span><br><span class="line">| 107 | 王尼玛 | 男 | 1976-02-20 | 95033 |</span><br><span class="line">| 101 | 曾华 | 男 | 1977-09-01 | 95033 |</span><br><span class="line">| 106 | 陆军 | 男 | 1974-06-03 | 95031 |</span><br><span class="line">| 109 | 赵铁柱 | 男 | 1974-06-03 | 95031 |</span><br><span class="line">| 105 | 王芳 | 女 | 1975-02-10 | 95031 |</span><br><span class="line">| 108 | 张全蛋 | 男 | 1975-02-10 | 95031 |</span><br><span class="line">| 102 | 匡明 | 男 | 1975-10-02 | 95031 |</span><br><span class="line">+-----+-----------+-----+------------+-------+</span><br></pre></td></tr></table></figure><h3 id="子查询-5"><a href="#子查询-5" class="headerlink" title="子查询 - 5"></a>子查询 - 5</h3><p><strong>查询 “男” 教师及其所上的课程。</strong></p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line">SELECT * FROM course WHERE t_no in (SELECT no FROM teacher WHERE sex = '男');</span><br><span class="line">+-------+--------------+------+</span><br><span class="line">| no | name | t_no |</span><br><span class="line">+-------+--------------+------+</span><br><span class="line">| 3-245 | 操作系统 | 804 |</span><br><span class="line">| 6-166 | 数字电路 | 856 |</span><br><span class="line">+-------+--------------+------+</span><br></pre></td></tr></table></figure><h3 id="MAX-函数与子查询"><a href="#MAX-函数与子查询" class="headerlink" title="MAX 函数与子查询"></a>MAX 函数与子查询</h3><p><strong>查询最高分同学的 <code>score</code> 表。</strong></p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line">-- 找出最高成绩（该查询只能有一个结果）</span><br><span class="line">SELECT MAX(degree) FROM score;</span><br><span class="line"></span><br><span class="line">-- 根据上面的条件筛选出所有最高成绩表，</span><br><span class="line">-- 该查询可能有多个结果，假设 degree 值多次符合条件。</span><br><span class="line">SELECT * FROM score WHERE degree = (SELECT MAX(degree) FROM score);</span><br><span class="line">+------+-------+--------+</span><br><span class="line">| s_no | c_no | degree |</span><br><span class="line">+------+-------+--------+</span><br><span class="line">| 103 | 3-105 | 92 |</span><br><span class="line">+------+-------+--------+</span><br></pre></td></tr></table></figure><h3 id="子查询-6"><a href="#子查询-6" class="headerlink" title="子查询 - 6"></a>子查询 - 6</h3><p><strong>查询和 “李军” 同性别的所有同学 <code>name</code> 。</strong></p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br></pre></td><td class="code"><pre><span class="line">-- 首先将李军的性别作为条件取出来</span><br><span class="line">SELECT sex FROM student WHERE name = '李军';</span><br><span class="line">+-----+</span><br><span class="line">| sex |</span><br><span class="line">+-----+</span><br><span class="line">| 男 |</span><br><span class="line">+-----+</span><br><span class="line"></span><br><span class="line">-- 根据性别查询 name 和 sex</span><br><span class="line">SELECT name, sex FROM student WHERE sex = (</span><br><span class="line"> SELECT sex FROM student WHERE name = '李军'</span><br><span class="line">);</span><br><span class="line">+-----------+-----+</span><br><span class="line">| name | sex |</span><br><span class="line">+-----------+-----+</span><br><span class="line">| 曾华 | 男 |</span><br><span class="line">| 匡明 | 男 |</span><br><span class="line">| 李军 | 男 |</span><br><span class="line">| 陆军 | 男 |</span><br><span class="line">| 王尼玛 | 男 |</span><br><span class="line">| 张全蛋 | 男 |</span><br><span class="line">| 赵铁柱 | 男 |</span><br><span class="line">| 张飞 | 男 |</span><br><span class="line">+-----------+-----+</span><br></pre></td></tr></table></figure><h3 id="子查询-7"><a href="#子查询-7" class="headerlink" title="子查询 - 7"></a>子查询 - 7</h3><p><strong>查询和 “李军” 同性别且同班的同学 <code>name</code> 。</strong></p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line">SELECT name, sex, class FROM student WHERE sex = (</span><br><span class="line"> SELECT sex FROM student WHERE name = '李军'</span><br><span class="line">) AND class = (</span><br><span class="line"> SELECT class FROM student WHERE name = '李军'</span><br><span class="line">);</span><br><span class="line">+-----------+-----+-------+</span><br><span class="line">| name | sex | class |</span><br><span class="line">+-----------+-----+-------+</span><br><span class="line">| 曾华 | 男 | 95033 |</span><br><span class="line">| 李军 | 男 | 95033 |</span><br><span class="line">| 王尼玛 | 男 | 95033 |</span><br><span class="line">+-----------+-----+-------+</span><br></pre></td></tr></table></figure><h3 id="子查询-8"><a href="#子查询-8" class="headerlink" title="子查询 - 8"></a>子查询 - 8</h3><p><strong>查询所有选修 “计算机导论” 课程的 “男” 同学成绩表。</strong></p><p>需要的 “计算机导论” 和性别为 “男” 的编号可以在 <code>course</code> 和 <code>student</code> 表中找到。</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br></pre></td><td class="code"><pre><span class="line">SELECT * FROM score WHERE c_no = (</span><br><span class="line"> SELECT no FROM course WHERE name = '计算机导论'</span><br><span class="line">) AND s_no IN (</span><br><span class="line"> SELECT no FROM student WHERE sex = '男'</span><br><span class="line">);</span><br><span class="line">+------+-------+--------+</span><br><span class="line">| s_no | c_no | degree |</span><br><span class="line">+------+-------+--------+</span><br><span class="line">| 101 | 3-105 | 90 |</span><br><span class="line">| 102 | 3-105 | 91 |</span><br><span class="line">| 104 | 3-105 | 89 |</span><br><span class="line">| 109 | 3-105 | 76 |</span><br><span class="line">+------+-------+--------+</span><br></pre></td></tr></table></figure><h3 id="按等级查询"><a href="#按等级查询" class="headerlink" title="按等级查询"></a>按等级查询</h3><p>建立一个 <code>grade</code> 表代表学生的成绩等级，并插入数据：</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br></pre></td><td class="code"><pre><span class="line">CREATE TABLE grade (</span><br><span class="line"> low INT(3),</span><br><span class="line"> upp INT(3),</span><br><span class="line"> grade char(1)</span><br><span class="line">);</span><br><span class="line"></span><br><span class="line">INSERT INTO grade VALUES (90, 100, 'A');</span><br><span class="line">INSERT INTO grade VALUES (80, 89, 'B');</span><br><span class="line">INSERT INTO grade VALUES (70, 79, 'C');</span><br><span class="line">INSERT INTO grade VALUES (60, 69, 'D');</span><br><span class="line">INSERT INTO grade VALUES (0, 59, 'E');</span><br><span class="line"></span><br><span class="line">SELECT * FROM grade;</span><br><span class="line">+------+------+-------+</span><br><span class="line">| low | upp | grade |</span><br><span class="line">+------+------+-------+</span><br><span class="line">| 90 | 100 | A |</span><br><span class="line">| 80 | 89 | B |</span><br><span class="line">| 70 | 79 | C |</span><br><span class="line">| 60 | 69 | D |</span><br><span class="line">| 0 | 59 | E |</span><br><span class="line">+------+------+-------+</span><br></pre></td></tr></table></figure><p><strong>查询所有学生的 <code>s_no</code> 、<code>c_no</code> 和 <code>grade</code> 列。</strong></p><p>思路是，使用区间 ( <code>BETWEEN</code> ) 查询，判断学生的成绩 ( <code>degree</code> ) 在 <code>grade</code> 表的 <code>low</code> 和 <code>upp</code> 之间。</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br></pre></td><td class="code"><pre><span class="line">SELECT s_no, c_no, grade FROM score, grade</span><br><span class="line">WHERE degree BETWEEN low AND upp;</span><br><span class="line">+------+-------+-------+</span><br><span class="line">| s_no | c_no | grade |</span><br><span class="line">+------+-------+-------+</span><br><span class="line">| 101 | 3-105 | A |</span><br><span class="line">| 102 | 3-105 | A |</span><br><span class="line">| 103 | 3-105 | A |</span><br><span class="line">| 103 | 3-245 | B |</span><br><span class="line">| 103 | 6-166 | B |</span><br><span class="line">| 104 | 3-105 | B |</span><br><span class="line">| 105 | 3-105 | B |</span><br><span class="line">| 105 | 3-245 | C |</span><br><span class="line">| 105 | 6-166 | C |</span><br><span class="line">| 109 | 3-105 | C |</span><br><span class="line">| 109 | 3-245 | D |</span><br><span class="line">| 109 | 6-166 | B |</span><br><span class="line">+------+-------+-------+</span><br></pre></td></tr></table></figure><h3 id="连接查询"><a href="#连接查询" class="headerlink" title="连接查询"></a>连接查询</h3><p>准备用于测试连接查询的数据：</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br></pre></td><td class="code"><pre><span class="line">CREATE DATABASE testJoin;</span><br><span class="line"></span><br><span class="line">CREATE TABLE person (</span><br><span class="line"> id INT,</span><br><span class="line"> name VARCHAR(20),</span><br><span class="line"> cardId INT</span><br><span class="line">);</span><br><span class="line"></span><br><span class="line">CREATE TABLE card (</span><br><span class="line"> id INT,</span><br><span class="line"> name VARCHAR(20)</span><br><span class="line">);</span><br><span class="line"></span><br><span class="line">INSERT INTO card VALUES (1, '饭卡'), (2, '建行卡'), (3, '农行卡'), (4, '工商卡'), (5, '邮政卡');</span><br><span class="line">SELECT * FROM card;</span><br><span class="line">+------+-----------+</span><br><span class="line">| id | name |</span><br><span class="line">+------+-----------+</span><br><span class="line">| 1 | 饭卡 |</span><br><span class="line">| 2 | 建行卡 |</span><br><span class="line">| 3 | 农行卡 |</span><br><span class="line">| 4 | 工商卡 |</span><br><span class="line">| 5 | 邮政卡 |</span><br><span class="line">+------+-----------+</span><br><span class="line"></span><br><span class="line">INSERT INTO person VALUES (1, '张三', 1), (2, '李四', 3), (3, '王五', 6);</span><br><span class="line">SELECT * FROM person;</span><br><span class="line">+------+--------+--------+</span><br><span class="line">| id | name | cardId |</span><br><span class="line">+------+--------+--------+</span><br><span class="line">| 1 | 张三 | 1 |</span><br><span class="line">| 2 | 李四 | 3 |</span><br><span class="line">| 3 | 王五 | 6 |</span><br><span class="line">+------+--------+--------+</span><br></pre></td></tr></table></figure><p>分析两张表发现，<code>person</code> 表并没有为 <code>cardId</code> 字段设置一个在 <code>card</code> 表中对应的 <code>id</code> 外键。如果设置了的话，<code>person</code> 中 <code>cardId</code> 字段值为 <code>6</code> 的行就插不进去，因为该 <code>cardId</code> 值在 <code>card</code> 表中并没有。</p><h4 id="内连接"><a href="#内连接" class="headerlink" title="内连接"></a>内连接</h4><p>要查询这两张表中有关系的数据，可以使用 <code>INNER JOIN</code> ( 内连接 ) 将它们连接在一起。</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line">-- INNER JOIN: 表示为内连接，将两张表拼接在一起。</span><br><span class="line">-- on: 表示要执行某个条件。</span><br><span class="line">SELECT * FROM person INNER JOIN card on person.cardId = card.id;</span><br><span class="line">+------+--------+--------+------+-----------+</span><br><span class="line">| id | name | cardId | id | name |</span><br><span class="line">+------+--------+--------+------+-----------+</span><br><span class="line">| 1 | 张三 | 1 | 1 | 饭卡 |</span><br><span class="line">| 2 | 李四 | 3 | 3 | 农行卡 |</span><br><span class="line">+------+--------+--------+------+-----------+</span><br><span class="line"></span><br><span class="line">-- 将 INNER 关键字省略掉，结果也是一样的。</span><br><span class="line">-- SELECT * FROM person JOIN card on person.cardId = card.id;</span><br></pre></td></tr></table></figure><blockquote><p>注意：<code>card</code> 的整张表被连接到了右边。</p></blockquote><h4 id="左外连接"><a href="#左外连接" class="headerlink" title="左外连接"></a>左外连接</h4><p>完整显示左边的表 ( <code>person</code> ) ，右边的表如果符合条件就显示，不符合则补 <code>NULL</code> 。</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line">-- LEFT JOIN 也叫做 LEFT OUTER JOIN，用这两种方式的查询结果是一样的。</span><br><span class="line">SELECT * FROM person LEFT JOIN card on person.cardId = card.id;</span><br><span class="line">+------+--------+--------+------+-----------+</span><br><span class="line">| id | name | cardId | id | name |</span><br><span class="line">+------+--------+--------+------+-----------+</span><br><span class="line">| 1 | 张三 | 1 | 1 | 饭卡 |</span><br><span class="line">| 2 | 李四 | 3 | 3 | 农行卡 |</span><br><span class="line">| 3 | 王五 | 6 | NULL | NULL |</span><br><span class="line">+------+--------+--------+------+-----------+</span><br></pre></td></tr></table></figure><h4 id="右外链接"><a href="#右外链接" class="headerlink" title="右外链接"></a>右外链接</h4><p>完整显示右边的表 ( <code>card</code> ) ，左边的表如果符合条件就显示，不符合则补 <code>NULL</code> 。</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line">SELECT * FROM person RIGHT JOIN card on person.cardId = card.id;</span><br><span class="line">+------+--------+--------+------+-----------+</span><br><span class="line">| id | name | cardId | id | name |</span><br><span class="line">+------+--------+--------+------+-----------+</span><br><span class="line">| 1 | 张三 | 1 | 1 | 饭卡 |</span><br><span class="line">| 2 | 李四 | 3 | 3 | 农行卡 |</span><br><span class="line">| NULL | NULL | NULL | 2 | 建行卡 |</span><br><span class="line">| NULL | NULL | NULL | 4 | 工商卡 |</span><br><span class="line">| NULL | NULL | NULL | 5 | 邮政卡 |</span><br><span class="line">+------+--------+--------+------+-----------+</span><br></pre></td></tr></table></figure><h4 id="全外链接"><a href="#全外链接" class="headerlink" title="全外链接"></a>全外链接</h4><p>完整显示两张表的全部数据。</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br></pre></td><td class="code"><pre><span class="line">-- MySQL 不支持这种语法的全外连接</span><br><span class="line">-- SELECT * FROM person FULL JOIN card on person.cardId = card.id;</span><br><span class="line">-- 出现错误：</span><br><span class="line">-- ERROR 1054 (42S22): Unknown column 'person.cardId' in 'on clause'</span><br><span class="line"></span><br><span class="line">-- MySQL全连接语法，使用 UNION 将两张表合并在一起。</span><br><span class="line">SELECT * FROM person LEFT JOIN card on person.cardId = card.id</span><br><span class="line">UNION</span><br><span class="line">SELECT * FROM person RIGHT JOIN card on person.cardId = card.id;</span><br><span class="line">+------+--------+--------+------+-----------+</span><br><span class="line">| id | name | cardId | id | name |</span><br><span class="line">+------+--------+--------+------+-----------+</span><br><span class="line">| 1 | 张三 | 1 | 1 | 饭卡 |</span><br><span class="line">| 2 | 李四 | 3 | 3 | 农行卡 |</span><br><span class="line">| 3 | 王五 | 6 | NULL | NULL |</span><br><span class="line">| NULL | NULL | NULL | 2 | 建行卡 |</span><br><span class="line">| NULL | NULL | NULL | 4 | 工商卡 |</span><br><span class="line">| NULL | NULL | NULL | 5 | 邮政卡 |</span><br><span class="line">+------+--------+--------+------+-----------+</span><br></pre></td></tr></table></figure><h2 id="事务"><a href="#事务" class="headerlink" title="事务"></a>事务</h2><p>在 MySQL 中，事务其实是一个最小的不可分割的工作单元。事务能够<strong>保证一个业务的完整性</strong>。</p><p>比如我们的银行转账：</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">-- a -> -100</span><br><span class="line">UPDATE user set money = money - 100 WHERE name = 'a';</span><br><span class="line"></span><br><span class="line">-- b -> +100</span><br><span class="line">UPDATE user set money = money + 100 WHERE name = 'b';</span><br></pre></td></tr></table></figure><p>在实际项目中，假设只有一条 SQL 语句执行成功，而另外一条执行失败了，就会出现数据前后不一致。</p><p>因此，在执行多条有关联 SQL 语句时，<strong>事务</strong>可能会要求这些 SQL 语句要么同时执行成功，要么就都执行失败。</p><h3 id="如何控制事务-COMMIT-ROLLBACK"><a href="#如何控制事务-COMMIT-ROLLBACK" class="headerlink" title="如何控制事务 - COMMIT / ROLLBACK"></a>如何控制事务 - COMMIT / ROLLBACK</h3><p>在 MySQL 中，事务的<strong>自动提交</strong>状态默认是开启的。</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line">-- 查询事务的自动提交状态</span><br><span class="line">SELECT @@AUTOCOMMIT;</span><br><span class="line">+--------------+</span><br><span class="line">| @@AUTOCOMMIT |</span><br><span class="line">+--------------+</span><br><span class="line">| 1 |</span><br><span class="line">+--------------+</span><br></pre></td></tr></table></figure><p><strong>自动提交的作用</strong>：当我们执行一条 SQL 语句的时候，其产生的效果就会立即体现出来，且不能<strong>回滚</strong>。</p><p>什么是回滚？举个例子：</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br></pre></td><td class="code"><pre><span class="line">CREATE DATABASE bank;</span><br><span class="line"></span><br><span class="line">USE bank;</span><br><span class="line"></span><br><span class="line">CREATE TABLE user (</span><br><span class="line"> id INT PRIMARY KEY,</span><br><span class="line"> name VARCHAR(20),</span><br><span class="line"> money INT</span><br><span class="line">);</span><br><span class="line"></span><br><span class="line">INSERT INTO user VALUES (1, 'a', 1000);</span><br><span class="line"></span><br><span class="line">SELECT * FROM user;</span><br><span class="line">+----+------+-------+</span><br><span class="line">| id | name | money |</span><br><span class="line">+----+------+-------+</span><br><span class="line">| 1 | a | 1000 |</span><br><span class="line">+----+------+-------+</span><br></pre></td></tr></table></figure><p>可以看到，在执行插入语句后数据立刻生效，原因是 MySQL 中的事务自动将它<strong>提交</strong>到了数据库中。那么所谓<strong>回滚</strong>的意思就是，撤销执行过的所有 SQL 语句，使其回滚到<strong>最后一次提交</strong>数据时的状态。</p><p>在 MySQL 中使用 <code>ROLLBACK</code> 执行回滚：</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line">-- 回滚到最后一次提交</span><br><span class="line">ROLLBACK;</span><br><span class="line"></span><br><span class="line">SELECT * FROM user;</span><br><span class="line">+----+------+-------+</span><br><span class="line">| id | name | money |</span><br><span class="line">+----+------+-------+</span><br><span class="line">| 1 | a | 1000 |</span><br><span class="line">+----+------+-------+</span><br></pre></td></tr></table></figure><p>由于所有执行过的 SQL 语句都已经被提交过了，所以数据并没有发生回滚。那如何让数据可以发生回滚？</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line">-- 关闭自动提交</span><br><span class="line">SET AUTOCOMMIT = 0;</span><br><span class="line"></span><br><span class="line">-- 查询自动提交状态</span><br><span class="line">SELECT @@AUTOCOMMIT;</span><br><span class="line">+--------------+</span><br><span class="line">| @@AUTOCOMMIT |</span><br><span class="line">+--------------+</span><br><span class="line">| 0 |</span><br><span class="line">+--------------+</span><br></pre></td></tr></table></figure><p>将自动提交关闭后，测试数据回滚：</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br></pre></td><td class="code"><pre><span class="line">INSERT INTO user VALUES (2, 'b', 1000);</span><br><span class="line"></span><br><span class="line">-- 关闭 AUTOCOMMIT 后，数据的变化是在一张虚拟的临时数据表中展示，</span><br><span class="line">-- 发生变化的数据并没有真正插入到数据表中。</span><br><span class="line">SELECT * FROM user;</span><br><span class="line">+----+------+-------+</span><br><span class="line">| id | name | money |</span><br><span class="line">+----+------+-------+</span><br><span class="line">| 1 | a | 1000 |</span><br><span class="line">| 2 | b | 1000 |</span><br><span class="line">+----+------+-------+</span><br><span class="line"></span><br><span class="line">-- 数据表中的真实数据其实还是：</span><br><span class="line">+----+------+-------+</span><br><span class="line">| id | name | money |</span><br><span class="line">+----+------+-------+</span><br><span class="line">| 1 | a | 1000 |</span><br><span class="line">+----+------+-------+</span><br><span class="line"></span><br><span class="line">-- 由于数据还没有真正提交，可以使用回滚</span><br><span class="line">ROLLBACK;</span><br><span class="line"></span><br><span class="line">-- 再次查询</span><br><span class="line">SELECT * FROM user;</span><br><span class="line">+----+------+-------+</span><br><span class="line">| id | name | money |</span><br><span class="line">+----+------+-------+</span><br><span class="line">| 1 | a | 1000 |</span><br><span class="line">+----+------+-------+</span><br></pre></td></tr></table></figure><p>那如何将虚拟的数据真正提交到数据库中？使用 <code>COMMIT</code> :</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br></pre></td><td class="code"><pre><span class="line">INSERT INTO user VALUES (2, 'b', 1000);</span><br><span class="line">-- 手动提交数据（持久性），</span><br><span class="line">-- 将数据真正提交到数据库中，执行后不能再回滚提交过的数据。</span><br><span class="line">COMMIT;</span><br><span class="line"></span><br><span class="line">-- 提交后测试回滚</span><br><span class="line">ROLLBACK;</span><br><span class="line"></span><br><span class="line">-- 再次查询（回滚无效了）</span><br><span class="line">SELECT * FROM user;</span><br><span class="line">+----+------+-------+</span><br><span class="line">| id | name | money |</span><br><span class="line">+----+------+-------+</span><br><span class="line">| 1 | a | 1000 |</span><br><span class="line">| 2 | b | 1000 |</span><br><span class="line">+----+------+-------+</span><br></pre></td></tr></table></figure><blockquote><p><strong>总结</strong></p><ol><li><p><strong>自动提交</strong></p><ul><li><p>查看自动提交状态：<code>SELECT @@AUTOCOMMIT</code> ；</p></li><li><p>设置自动提交状态：<code>SET AUTOCOMMIT = 0</code> 。</p></li></ul></li><li><p><strong>手动提交</strong></p><p><code>@@AUTOCOMMIT = 0</code> 时，使用 <code>COMMIT</code> 命令提交事务。</p></li><li><p><strong>事务回滚</strong></p><p><code>@@AUTOCOMMIT = 0</code> 时，使用 <code>ROLLBACK</code> 命令回滚事务。</p></li></ol></blockquote><p><strong>事务的实际应用</strong>，让我们再回到银行转账项目：</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br></pre></td><td class="code"><pre><span class="line">-- 转账</span><br><span class="line">UPDATE user set money = money - 100 WHERE name = 'a';</span><br><span class="line"></span><br><span class="line">-- 到账</span><br><span class="line">UPDATE user set money = money + 100 WHERE name = 'b';</span><br><span class="line"></span><br><span class="line">SELECT * FROM user;</span><br><span class="line">+----+------+-------+</span><br><span class="line">| id | name | money |</span><br><span class="line">+----+------+-------+</span><br><span class="line">| 1 | a | 900 |</span><br><span class="line">| 2 | b | 1100 |</span><br><span class="line">+----+------+-------+</span><br></pre></td></tr></table></figure><p>这时假设在转账时发生了意外，就可以使用 <code>ROLLBACK</code> 回滚到最后一次提交的状态：</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line">-- 假设转账发生了意外，需要回滚。</span><br><span class="line">ROLLBACK;</span><br><span class="line"></span><br><span class="line">SELECT * FROM user;</span><br><span class="line">+----+------+-------+</span><br><span class="line">| id | name | money |</span><br><span class="line">+----+------+-------+</span><br><span class="line">| 1 | a | 1000 |</span><br><span class="line">| 2 | b | 1000 |</span><br><span class="line">+----+------+-------+</span><br></pre></td></tr></table></figure><p>这时我们又回到了发生意外之前的状态，也就是说，事务给我们提供了一个可以反悔的机会。假设数据没有发生意外，这时可以手动将数据真正提交到数据表中：<code>COMMIT</code> 。</p><h3 id="手动开启事务-BEGIN-START-TRANSACTION"><a href="#手动开启事务-BEGIN-START-TRANSACTION" class="headerlink" title="手动开启事务 - BEGIN / START TRANSACTION"></a>手动开启事务 - BEGIN / START TRANSACTION</h3><p>事务的默认提交被开启 ( <code>@@AUTOCOMMIT = 1</code> ) 后，此时就不能使用事务回滚了。但是我们还可以手动开启一个事务处理事件，使其可以发生回滚：</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br></pre></td><td class="code"><pre><span class="line">-- 使用 BEGIN 或者 START TRANSACTION 手动开启一个事务</span><br><span class="line">-- START TRANSACTION;</span><br><span class="line">BEGIN;</span><br><span class="line">UPDATE user set money = money - 100 WHERE name = 'a';</span><br><span class="line">UPDATE user set money = money + 100 WHERE name = 'b';</span><br><span class="line"></span><br><span class="line">-- 由于手动开启的事务没有开启自动提交，</span><br><span class="line">-- 此时发生变化的数据仍然是被保存在一张临时表中。</span><br><span class="line">SELECT * FROM user;</span><br><span class="line">+----+------+-------+</span><br><span class="line">| id | name | money |</span><br><span class="line">+----+------+-------+</span><br><span class="line">| 1 | a | 900 |</span><br><span class="line">| 2 | b | 1100 |</span><br><span class="line">+----+------+-------+</span><br><span class="line"></span><br><span class="line">-- 测试回滚</span><br><span class="line">ROLLBACK;</span><br><span class="line"></span><br><span class="line">SELECT * FROM user;</span><br><span class="line">+----+------+-------+</span><br><span class="line">| id | name | money |</span><br><span class="line">+----+------+-------+</span><br><span class="line">| 1 | a | 1000 |</span><br><span class="line">| 2 | b | 1000 |</span><br><span class="line">+----+------+-------+</span><br></pre></td></tr></table></figure><p>仍然使用 <code>COMMIT</code> 提交数据，提交后无法再发生本次事务的回滚。</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br></pre></td><td class="code"><pre><span class="line">BEGIN;</span><br><span class="line">UPDATE user set money = money - 100 WHERE name = 'a';</span><br><span class="line">UPDATE user set money = money + 100 WHERE name = 'b';</span><br><span class="line"></span><br><span class="line">SELECT * FROM user;</span><br><span class="line">+----+------+-------+</span><br><span class="line">| id | name | money |</span><br><span class="line">+----+------+-------+</span><br><span class="line">| 1 | a | 900 |</span><br><span class="line">| 2 | b | 1100 |</span><br><span class="line">+----+------+-------+</span><br><span class="line"></span><br><span class="line">-- 提交数据</span><br><span class="line">COMMIT;</span><br><span class="line"></span><br><span class="line">-- 测试回滚（无效，因为表的数据已经被提交）</span><br><span class="line">ROLLBACK;</span><br></pre></td></tr></table></figure><h3 id="事务的-ACID-特征与使用"><a href="#事务的-ACID-特征与使用" class="headerlink" title="事务的 ACID 特征与使用"></a>事务的 ACID 特征与使用</h3><p><strong>事务的四大特征：</strong></p><ul><li><strong>A 原子性</strong>：事务是最小的单位，不可以再分割；</li><li><strong>C 一致性</strong>：要求同一事务中的 SQL 语句，必须保证同时成功或者失败；</li><li><strong>I 隔离性</strong>：事务1 和 事务2 之间是具有隔离性的；</li><li><strong>D 持久性</strong>：事务一旦结束 ( <code>COMMIT</code> ) ，就不可以再返回了 ( <code>ROLLBACK</code> ) 。</li></ul><h3 id="事务的隔离性"><a href="#事务的隔离性" class="headerlink" title="事务的隔离性"></a>事务的隔离性</h3><p><strong>事务的隔离性可分为四种 ( 性能从低到高 )</strong> ：</p><ol><li><p><strong>READ UNCOMMITTED ( 读取未提交 )</strong></p><p>如果有多个事务，那么任意事务都可以看见其他事务的<strong>未提交数据</strong>。</p></li><li><p><strong>READ COMMITTED ( 读取已提交 )</strong></p><p>只能读取到其他事务<strong>已经提交的数据</strong>。</p></li><li><p><strong>REPEATABLE READ ( 可被重复读 )</strong></p><p>如果有多个连接都开启了事务，那么事务之间不能共享数据记录，否则只能共享已提交的记录。</p></li><li><p><strong>SERIALIZABLE ( 串行化 )</strong></p><p>所有的事务都会按照<strong>固定顺序执行</strong>，执行完一个事务后再继续执行下一个事务的<strong>写入操作</strong>。</p></li></ol><p>查看当前数据库的默认隔离级别：</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line">-- MySQL 8.x, GLOBAL 表示系统级别，不加表示会话级别。</span><br><span class="line">SELECT @@GLOBAL.TRANSACTION_ISOLATION;</span><br><span class="line">SELECT @@TRANSACTION_ISOLATION;</span><br><span class="line">+--------------------------------+</span><br><span class="line">| @@GLOBAL.TRANSACTION_ISOLATION |</span><br><span class="line">+--------------------------------+</span><br><span class="line">| REPEATABLE-READ | -- MySQL的默认隔离级别，可以重复读。</span><br><span class="line">+--------------------------------+</span><br><span class="line"></span><br><span class="line">-- MySQL 5.x</span><br><span class="line">SELECT @@GLOBAL.TX_ISOLATION;</span><br><span class="line">SELECT @@TX_ISOLATION;</span><br></pre></td></tr></table></figure><p>修改隔离级别：</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line">-- 设置系统隔离级别，LEVEL 后面表示要设置的隔离级别 (READ UNCOMMITTED)。</span><br><span class="line">SET GLOBAL TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;</span><br><span class="line"></span><br><span class="line">-- 查询系统隔离级别，发现已经被修改。</span><br><span class="line">SELECT @@GLOBAL.TRANSACTION_ISOLATION;</span><br><span class="line">+--------------------------------+</span><br><span class="line">| @@GLOBAL.TRANSACTION_ISOLATION |</span><br><span class="line">+--------------------------------+</span><br><span class="line">| READ-UNCOMMITTED |</span><br><span class="line">+--------------------------------+</span><br></pre></td></tr></table></figure><h4 id="脏读"><a href="#脏读" class="headerlink" title="脏读"></a>脏读</h4><p>测试 <strong>READ UNCOMMITTED ( 读取未提交 )</strong> 的隔离性：</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br></pre></td><td class="code"><pre><span class="line">INSERT INTO user VALUES (3, '小明', 1000);</span><br><span class="line">INSERT INTO user VALUES (4, '淘宝店', 1000);</span><br><span class="line"></span><br><span class="line">SELECT * FROM user;</span><br><span class="line">+----+-----------+-------+</span><br><span class="line">| id | name | money |</span><br><span class="line">+----+-----------+-------+</span><br><span class="line">| 1 | a | 900 |</span><br><span class="line">| 2 | b | 1100 |</span><br><span class="line">| 3 | 小明 | 1000 |</span><br><span class="line">| 4 | 淘宝店 | 1000 |</span><br><span class="line">+----+-----------+-------+</span><br><span class="line"></span><br><span class="line">-- 开启一个事务操作数据</span><br><span class="line">-- 假设小明在淘宝店买了一双800块钱的鞋子：</span><br><span class="line">START TRANSACTION;</span><br><span class="line">UPDATE user SET money = money - 800 WHERE name = '小明';</span><br><span class="line">UPDATE user SET money = money + 800 WHERE name = '淘宝店';</span><br><span class="line"></span><br><span class="line">-- 然后淘宝店在另一方查询结果，发现钱已到账。</span><br><span class="line">SELECT * FROM user;</span><br><span class="line">+----+-----------+-------+</span><br><span class="line">| id | name | money |</span><br><span class="line">+----+-----------+-------+</span><br><span class="line">| 1 | a | 900 |</span><br><span class="line">| 2 | b | 1100 |</span><br><span class="line">| 3 | 小明 | 200 |</span><br><span class="line">| 4 | 淘宝店 | 1800 |</span><br><span class="line">+----+-----------+-------+</span><br></pre></td></tr></table></figure><p>由于小明的转账是在新开启的事务上进行操作的，而该操作的结果是可以被其他事务（另一方的淘宝店）看见的，因此淘宝店的查询结果是正确的，淘宝店确认到账。但就在这时，如果小明在它所处的事务上又执行了 <code>ROLLBACK</code> 命令，会发生什么？</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br></pre></td><td class="code"><pre><span class="line">-- 小明所处的事务</span><br><span class="line">ROLLBACK;</span><br><span class="line"></span><br><span class="line">-- 此时无论对方是谁，如果再去查询结果就会发现：</span><br><span class="line">SELECT * FROM user;</span><br><span class="line">+----+-----------+-------+</span><br><span class="line">| id | name | money |</span><br><span class="line">+----+-----------+-------+</span><br><span class="line">| 1 | a | 900 |</span><br><span class="line">| 2 | b | 1100 |</span><br><span class="line">| 3 | 小明 | 1000 |</span><br><span class="line">| 4 | 淘宝店 | 1000 |</span><br><span class="line">+----+-----------+-------+</span><br></pre></td></tr></table></figure><p>这就是所谓的<strong>脏读</strong>，一个事务读取到另外一个事务还未提交的数据。这在实际开发中是不允许出现的。</p><h4 id="读取已提交"><a href="#读取已提交" class="headerlink" title="读取已提交"></a>读取已提交</h4><p>把隔离级别设置为 <strong>READ COMMITTED</strong> ：</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line">SET GLOBAL TRANSACTION ISOLATION LEVEL READ COMMITTED;</span><br><span class="line">SELECT @@GLOBAL.TRANSACTION_ISOLATION;</span><br><span class="line">+--------------------------------+</span><br><span class="line">| @@GLOBAL.TRANSACTION_ISOLATION |</span><br><span class="line">+--------------------------------+</span><br><span class="line">| READ-COMMITTED |</span><br><span class="line">+--------------------------------+</span><br></pre></td></tr></table></figure><p>这样，再有新的事务连接进来时，它们就只能查询到已经提交过的事务数据了。但是对于当前事务来说，它们看到的还是未提交的数据，例如：</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br></pre></td><td class="code"><pre><span class="line">-- 正在操作数据事务（当前事务）</span><br><span class="line">START TRANSACTION;</span><br><span class="line">UPDATE user SET money = money - 800 WHERE name = '小明';</span><br><span class="line">UPDATE user SET money = money + 800 WHERE name = '淘宝店';</span><br><span class="line"></span><br><span class="line">-- 虽然隔离级别被设置为了 READ COMMITTED，但在当前事务中，</span><br><span class="line">-- 它看到的仍然是数据表中临时改变数据，而不是真正提交过的数据。</span><br><span class="line">SELECT * FROM user;</span><br><span class="line">+----+-----------+-------+</span><br><span class="line">| id | name | money |</span><br><span class="line">+----+-----------+-------+</span><br><span class="line">| 1 | a | 900 |</span><br><span class="line">| 2 | b | 1100 |</span><br><span class="line">| 3 | 小明 | 200 |</span><br><span class="line">| 4 | 淘宝店 | 1800 |</span><br><span class="line">+----+-----------+-------+</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">-- 假设此时在远程开启了一个新事务，连接到数据库。</span><br><span class="line">$ mysql -u root -p12345612</span><br><span class="line"></span><br><span class="line">-- 此时远程连接查询到的数据只能是已经提交过的</span><br><span class="line">SELECT * FROM user;</span><br><span class="line">+----+-----------+-------+</span><br><span class="line">| id | name | money |</span><br><span class="line">+----+-----------+-------+</span><br><span class="line">| 1 | a | 900 |</span><br><span class="line">| 2 | b | 1100 |</span><br><span class="line">| 3 | 小明 | 1000 |</span><br><span class="line">| 4 | 淘宝店 | 1000 |</span><br><span class="line">+----+-----------+-------+</span><br></pre></td></tr></table></figure><p>但是这样还有问题，那就是假设一个事务在操作数据时，其他事务干扰了这个事务的数据。例如：</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br></pre></td><td class="code"><pre><span class="line">-- 小张在查询数据的时候发现：</span><br><span class="line">SELECT * FROM user;</span><br><span class="line">+----+-----------+-------+</span><br><span class="line">| id | name | money |</span><br><span class="line">+----+-----------+-------+</span><br><span class="line">| 1 | a | 900 |</span><br><span class="line">| 2 | b | 1100 |</span><br><span class="line">| 3 | 小明 | 200 |</span><br><span class="line">| 4 | 淘宝店 | 1800 |</span><br><span class="line">+----+-----------+-------+</span><br><span class="line"></span><br><span class="line">-- 在小张求表的 money 平均值之前，小王做了一个操作：</span><br><span class="line">START TRANSACTION;</span><br><span class="line">INSERT INTO user VALUES (5, 'c', 100);</span><br><span class="line">COMMIT;</span><br><span class="line"></span><br><span class="line">-- 此时表的真实数据是：</span><br><span class="line">SELECT * FROM user;</span><br><span class="line">+----+-----------+-------+</span><br><span class="line">| id | name | money |</span><br><span class="line">+----+-----------+-------+</span><br><span class="line">| 1 | a | 900 |</span><br><span class="line">| 2 | b | 1100 |</span><br><span class="line">| 3 | 小明 | 1000 |</span><br><span class="line">| 4 | 淘宝店 | 1000 |</span><br><span class="line">| 5 | c | 100 |</span><br><span class="line">+----+-----------+-------+</span><br><span class="line"></span><br><span class="line">-- 这时小张再求平均值的时候，就会出现计算不相符合的情况：</span><br><span class="line">SELECT AVG(money) FROM user;</span><br><span class="line">+------------+</span><br><span class="line">| AVG(money) |</span><br><span class="line">+------------+</span><br><span class="line">| 820.0000 |</span><br><span class="line">+------------+</span><br></pre></td></tr></table></figure><p>虽然 <strong>READ COMMITTED</strong> 让我们只能读取到其他事务已经提交的数据，但还是会出现问题，就是<strong>在读取同一个表的数据时，可能会发生前后不一致的情况。</strong>这被称为<strong>不可重复读现象 ( READ COMMITTED )</strong> 。</p><h4 id="幻读"><a href="#幻读" class="headerlink" title="幻读"></a>幻读</h4><p>将隔离级别设置为 <strong>REPEATABLE READ ( 可被重复读取 )</strong> :</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line">SET GLOBAL TRANSACTION ISOLATION LEVEL REPEATABLE READ;</span><br><span class="line">SELECT @@GLOBAL.TRANSACTION_ISOLATION;</span><br><span class="line">+--------------------------------+</span><br><span class="line">| @@GLOBAL.TRANSACTION_ISOLATION |</span><br><span class="line">+--------------------------------+</span><br><span class="line">| REPEATABLE-READ |</span><br><span class="line">+--------------------------------+</span><br></pre></td></tr></table></figure><p>测试 <strong>REPEATABLE READ</strong> ，假设在两个不同的连接上分别执行 <code>START TRANSACTION</code> :</p><figure class="highlight sql"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">-- 小张 - 成都</span></span><br><span class="line"><span class="keyword">START</span> TRANSACTION;</span><br><span class="line"><span class="keyword">INSERT</span> <span class="keyword">INTO</span> <span class="keyword">user</span> <span class="keyword">VALUES</span> (<span class="number">6</span>, <span class="string">'d'</span>, <span class="number">1000</span>);</span><br><span class="line"></span><br><span class="line"><span class="comment">-- 小王 - 北京</span></span><br><span class="line"><span class="keyword">START</span> TRANSACTION;</span><br><span class="line"></span><br><span class="line"><span class="comment">-- 小张 - 成都</span></span><br><span class="line"><span class="keyword">COMMIT</span>;</span><br></pre></td></tr></table></figure><p>当前事务开启后，没提交之前，查询不到，提交后可以被查询到。但是，在提交之前其他事务被开启了，那么在这条事务线上，就不会查询到当前有操作事务的连接。相当于开辟出一条单独的线程。</p><p>无论小张是否执行过 <code>COMMIT</code> ，在小王这边，都不会查询到小张的事务记录，而是只会查询到自己所处事务的记录：</p><figure class="highlight sql"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">SELECT</span> <span class="operator">*</span> <span class="keyword">FROM</span> <span class="keyword">user</span>;</span><br><span class="line"><span class="operator">+</span><span class="comment">----+-----------+-------+</span></span><br><span class="line"><span class="operator">|</span> id <span class="operator">|</span> name <span class="operator">|</span> money <span class="operator">|</span></span><br><span class="line"><span class="operator">+</span><span class="comment">----+-----------+-------+</span></span><br><span class="line"><span class="operator">|</span> <span class="number">1</span> <span class="operator">|</span> a <span class="operator">|</span> <span class="number">900</span> <span class="operator">|</span></span><br><span class="line"><span class="operator">|</span> <span class="number">2</span> <span class="operator">|</span> b <span class="operator">|</span> <span class="number">1100</span> <span class="operator">|</span></span><br><span class="line"><span class="operator">|</span> <span class="number">3</span> <span class="operator">|</span> 小明 <span class="operator">|</span> <span class="number">1000</span> <span class="operator">|</span></span><br><span class="line"><span class="operator">|</span> <span class="number">4</span> <span class="operator">|</span> 淘宝店 <span class="operator">|</span> <span class="number">1000</span> <span class="operator">|</span></span><br><span class="line"><span class="operator">|</span> <span class="number">5</span> <span class="operator">|</span> c <span class="operator">|</span> <span class="number">100</span> <span class="operator">|</span></span><br><span class="line"><span class="operator">+</span><span class="comment">----+-----------+-------+</span></span><br></pre></td></tr></table></figure><p>这是<strong>因为小王在此之前开启了一个新的事务 ( <code>START TRANSACTION</code> )</strong>，那么<strong>在他的这条新事务的线上，跟其他事务是没有联系的</strong>，也就是说，此时如果其他事务正在操作数据，它是不知道的。</p><p>然而事实是，在真实的数据表中，小张已经插入了一条数据。但是小王此时并不知道，也插入了同一条数据，会发生什么呢？</p><figure class="highlight sql"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">INSERT</span> <span class="keyword">INTO</span> <span class="keyword">user</span> <span class="keyword">VALUES</span> (<span class="number">6</span>, <span class="string">'d'</span>, <span class="number">1000</span>);</span><br><span class="line"><span class="comment">-- ERROR 1062 (23000): Duplicate entry '6' for key 'PRIMARY'</span></span><br></pre></td></tr></table></figure><p>报错了，操作被告知已存在主键为 <code>6</code> 的字段。这种现象也被称为<strong>幻读，一个事务提交的数据，不能被其他事务读取到</strong>。</p><h4 id="串行化"><a href="#串行化" class="headerlink" title="串行化"></a>串行化</h4><p>顾名思义，就是所有事务的<strong>写入操作</strong>全都是串行化的。什么意思？把隔离级别修改成 <strong>SERIALIZABLE</strong> :</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line">SET GLOBAL TRANSACTION ISOLATION LEVEL SERIALIZABLE;</span><br><span class="line">SELECT @@GLOBAL.TRANSACTION_ISOLATION;</span><br><span class="line">+--------------------------------+</span><br><span class="line">| @@GLOBAL.TRANSACTION_ISOLATION |</span><br><span class="line">+--------------------------------+</span><br><span class="line">| SERIALIZABLE |</span><br><span class="line">+--------------------------------+</span><br></pre></td></tr></table></figure><p>还是拿小张和小王来举例：</p><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br></pre></td><td class="code"><pre><span class="line">-- 小张 - 成都</span><br><span class="line">START TRANSACTION;</span><br><span class="line"></span><br><span class="line">-- 小王 - 北京</span><br><span class="line">START TRANSACTION;</span><br><span class="line"></span><br><span class="line">-- 开启事务之前先查询表，准备操作数据。</span><br><span class="line">SELECT * FROM user;</span><br><span class="line">+----+-----------+-------+</span><br><span class="line">| id | name | money |</span><br><span class="line">+----+-----------+-------+</span><br><span class="line">| 1 | a | 900 |</span><br><span class="line">| 2 | b | 1100 |</span><br><span class="line">| 3 | 小明 | 1000 |</span><br><span class="line">| 4 | 淘宝店 | 1000 |</span><br><span class="line">| 5 | c | 100 |</span><br><span class="line">| 6 | d | 1000 |</span><br><span class="line">+----+-----------+-------+</span><br><span class="line"></span><br><span class="line">-- 发现没有 7 号王小花，于是插入一条数据：</span><br><span class="line">INSERT INTO user VALUES (7, '王小花', 1000);</span><br></pre></td></tr></table></figure><p>此时会发生什么呢？由于现在的隔离级别是 <strong>SERIALIZABLE ( 串行化 )</strong> ，串行化的意思就是：假设把所有的事务都放在一个串行的队列中，那么所有的事务都会按照<strong>固定顺序执行</strong>，执行完一个事务后再继续执行下一个事务的<strong>写入操作</strong> ( <strong>这意味着队列中同时只能执行一个事务的写入操作</strong> ) 。</p><p>根据这个解释，小王在插入数据时，会出现等待状态，直到小张执行 <code>COMMIT</code> 结束它所处的事务，或者出现等待超时。</p>]]></content>
<categories>
<category> 编程 </category>
</categories>
<tags>
<tag> MySQL </tag>
</tags>
</entry>
<entry>
<title>Hello,World！</title>
<link href="/posts/0.html"/>
<url>/posts/0.html</url>
<content type="html"><![CDATA[<!-- markdownlint-disable MD025 MD026 --><h1 id="Hello，World"><a href="#Hello，World" class="headerlink" title="Hello，World!"></a>Hello，World!</h1>]]></content>
<categories>
<category> 日常 </category>
</categories>
<tags>
<tag> Hello，World </tag>
</tags>
</entry>
<entry>
<title>分类</title>
<link href="/categories/index.html"/>
<url>/categories/index.html</url>
<content type="html"><![CDATA[]]></content>
</entry>
<entry>
<title></title>
<link href="/css/custom.css"/>
<url>/css/custom.css</url>
<content type="html"><![CDATA[/* @font-face { font-family: Candyhome; src: url(https://npm.elemecdn.com/[email protected]/fonts/Candyhome.ttf); font-display: swap; font-weight: lighter;} */@font-face { font-family: ZhuZiAYuanJWD; src: url(https://npm.elemecdn.com/[email protected]/fonts/ZhuZiAWan.woff2); font-display: swap; font-weight: lighter; } div#menus { font-family: 'ZhuZiAYuanJWD'; } h1#site-title { font-family: ZhuZiAYuanJWD; font-size: 3em !important; } a.article-title, a.blog-slider__title, a.categoryBar-list-link, h1.post-title { font-family: ZhuZiAYuanJWD; } .iconfont { font-family: 'iconfont' !important; font-size: 3em; /* 可以定义图标大小 */ font-style: normal; -webkit-font-smoothing: antialiased; -moz-osx-font-smoothing: grayscale; } /* 时间轴生肖icon */ svg.icon { /* 这里定义svg.icon，避免和Butterfly自带的note标签冲突 */ width: 1em; height: 1em; /* width和height定义图标的默认宽度和高度*/ vertical-align: -0.15em; fill: currentColor; overflow: hidden; } .icon-zhongbiao::before { color: #f7c768; } /* bilibli番剧插件 */ .bangumi-active { background: #dbecfe !important; border-radius: 10px !important; } a.bangumi-tab:hover { text-decoration: none !important; } .bangumi-button:hover { background: #dbecfe !important; border-radius: 10px !important; } a.bangumi-button.bangumi-nextpage:hover { text-decoration: none !important; } .bangumi-button { padding: 5px 10px !important; } a.bangumi-tab { padding: 5px 10px !important; } svg.icon.faa-tada { font-size: 1.1em; } /* 解决artitalk的图标问题 */ #uploadSource > svg { width: 1.19em; height: 1.5em; } /*top-img黑色透明玻璃效果移除，不建议加，除非你执着于完全一图流或者背景图对比色明显 */ #page-header:not(.not-top-img):before { background-color: transparent !important; } /* 首页文章卡片 */ #recent-posts > .recent-post-item { background: rgba(255, 255, 255, 0.9); } /* 首页侧栏卡片 */ #aside-content .card-widget { background: rgba(255, 255, 255, 0.9); } /* 文章页面正文背景 */ div#post { background: rgba(255, 255, 255, 0.9); } /* 分页页面 */ div#page { background: rgba(255, 255, 255, 0.9); } /* 归档页面 */ div#archive { background: rgba(255, 255, 255, 0.9); } /* 标签页面 */ div#tag { background: rgba(255, 255, 255, 0.9); } /* 分类页面 */ div#category { background: rgba(255, 255, 255, 0.9); } /*夜间模式伪类遮罩层透明*/ [data-theme='dark'] #recent-posts > .recent-post-item { background: #121212; } [data-theme='dark'] .card-widget { background: #121212 !important; } [data-theme='dark'] div#post { background: #121212 !important; } [data-theme='dark'] div#tag { background: #121212 !important; } [data-theme='dark'] div#archive { background: #121212 !important; } [data-theme='dark'] div#page { background: #121212 !important; } [data-theme='dark'] div#category { background: #121212 !important; } [data-theme='dark'] div#category { background: transparent !important; } /* 页脚透明 */ #footer { background: transparent !important; } /* 头图透明 */ #page-header { background: transparent !important; } #rightside > div > button { border-radius: 5px; } /* 滚动条 */ ::-webkit-scrollbar { width: 10px; height: 10px; } ::-webkit-scrollbar-thumb { background-color: #49b1f5; border-radius: 2em; } ::-webkit-scrollbar-corner { background-color: transparent; } ::-moz-selection { color: #fff; background-color: #49b1f5; } /* 音乐播放器 */ /* .aplayer .aplayer-lrc { display: none !important; } */ .aplayer.aplayer-fixed.aplayer-narrow .aplayer-body { left: -66px !important; transition: all 0.3s; /* 默认情况下缩进左侧66px，只留一点箭头部分 */ } .aplayer.aplayer-fixed.aplayer-narrow .aplayer-body:hover { left: 0 !important; transition: all 0.3s; /* 鼠标悬停是左侧缩进归零，完全显示按钮 */ } .aplayer.aplayer-fixed { z-index: 999999 !important; } /* 评论框 */ .vwrap { box-shadow: 2px 2px 5px #bbb; background: rgba(255, 255, 255, 0.3); border-radius: 8px; padding: 30px; margin: 30px 0px 30px 0px; } /* 设置评论框 */ .vcard { box-shadow: 2px 2px 5px #bbb; background: rgba(255, 255, 255, 0.3); border-radius: 8px; padding: 30px; margin: 30px 0px 0px 0px; } /* 鼠标图标 */ body { cursor: url('/img/arrow.cur'), auto; } a, [type='button']:not(:disabled), [type='reset']:not(:disabled), [type='submit']:not(:disabled), button:not(:disabled) { cursor: url('/img/x2.cur'), auto !important; } /* md网站下划线 */ #article-container a:hover { text-decoration: none !important; } #article-container #hpp_talk p img { display: inline; } /* 404页面 */ #error-wrap { position: absolute; top: 40%; right: 0; left: 0; margin: 0 auto; padding: 0 1rem; max-width: 1000px; transform: translate(0, -50%); } #error-wrap .error-content { display: flex; flex-direction: row; justify-content: center; align-items: center; margin: 0 1rem; height: 18rem; border-radius: 8px; background: var(--card-bg); box-shadow: var(--card-box-shadow); transition: all 0.3s; } #error-wrap .error-content .error-img { box-flex: 1; flex: 1; height: 100%; border-top-left-radius: 8px; border-bottom-left-radius: 8px; background-color: #49b1f5; background-position: center; background-size: cover; } #error-wrap .error-content .error-info { box-flex: 1; flex: 1; padding: 0.5rem; text-align: center; font-size: 14px; font-family: Titillium Web, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft JhengHei', 'Microsoft YaHei', sans-serif; } #error-wrap .error-content .error-info .error_title { margin-top: -4rem; font-size: 9em; } #error-wrap .error-content .error-info .error_subtitle { margin-top: -3.5rem; word-break: break-word; font-size: 1.6em; } #error-wrap .error-content .error-info a { display: inline-block; margin-top: 0.5rem; padding: 0.3rem 1.5rem; background: var(--btn-bg); color: var(--btn-color); } #body-wrap.error .aside-list { display: flex; flex-direction: row; flex-wrap: nowrap; bottom: 0px; position: absolute; padding: 1rem; width: 100%; overflow: scroll; } #body-wrap.error .aside-list .aside-list-group { display: flex; flex-direction: row; flex-wrap: nowrap; max-width: 1200px; margin: 0 auto; } #body-wrap.error .aside-list .aside-list-item { padding: 0.5rem; } #body-wrap.error .aside-list .aside-list-item img { width: 100%; object-fit: cover; border-radius: 12px; } #body-wrap.error .aside-list .aside-list-item .thumbnail { overflow: hidden; width: 230px; height: 143px; background: var(--heo-card-bg); display: flex; } #body-wrap.error .aside-list .aside-list-item .content .title { -webkit-line-clamp: 2; overflow: hidden; display: -webkit-box; -webkit-box-orient: vertical; line-height: 1.5; justify-content: center; align-items: flex-end; align-content: center; padding-top: 0.5rem; color: white; } #body-wrap.error .aside-list .aside-list-item .content time { display: none; } /* 代码框主题 */ #article-container figure.highlight { border-radius: 10px; }]]></content>
</entry>
<entry>
<title></title>
<link href="/js/gitcalendar.js"/>
<url>/js/gitcalendar.js</url>
<content type="html"><![CDATA[function GitCalendarInit(git_gitapiurl, git_color, git_user) { // 由于 git_gitapiurl 为https://python-github-calendar-api-lake-six.vercel.app/api?Alleyway-boop // 我们需要将 修改参数为 https://python-github-calendar-api-lake-six.vercel.app/api?user=Alleyway-boop 这样的形式 保留?前面的部分，后面的部分移除 git_gitapiurl = git_gitapiurl.split('?')[0] + '?user=' + git_user if (document.getElementById('git_container')) { var git_canlendar = (git_user, git_gitapiurl, git_color) => { var git_fixed = 'fixed'; var git_px = 'px'; var git_month = ['一月', '二月', '三月', '四月', '五月', '六月', '七月', '八月', '九月', '十月', '十一月', '十二月']; var git_monthchange = []; var git_oneyearbeforeday = ''; var git_thisday = ''; var git_amonthago = ''; var git_aweekago = ''; var git_weekdatacore = 0; var git_datacore = 0; var git_total = 0; var git_datadate = ''; var git_git_data = []; var git_positionplusdata = []; var git_firstweek = []; var git_lastweek = []; var git_beforeweek = []; var git_thisweekdatacore = 0; var git_mounthbeforeday = 0; var git_mounthfirstindex = 0; var git_crispedges = 'crispedges'; var git_thisdayindex = 0; var git_amonthagoindex = 0; var git_amonthagoweek = []; var git_firstdate = []; var git_first2date = []; var git_montharrbefore = []; var git_monthindex = 0; var retinaCanvas = (canvas, context, ratio) => { if (ratio > 1) { var canvasWidth = canvas.width; var canvasHeight = canvas.height; canvas.width = canvasWidth * ratio; canvas.height = canvasHeight * ratio; canvas.style.width = '100%'; canvas.style.height = canvasHeight + 'px'; context.scale(ratio, ratio); } } var responsiveChart = () => { if (document.getElementById("gitcanvas")) { var git_tooltip_container = document.getElementById('git_tooltip_container'); var ratio = window.devicePixelRatio || 1 var git_x = ''; var git_y = ''; var git_span1 = ''; var git_span2 = ''; var git_calendar_c = document.getElementById("gitcanvas"); git_calendar_c.style.width = '100%'; git_calendar_c.style.height = ''; var cmessage = document.getElementById("gitmessage"); var git_calendar_ctx = git_calendar_c.getContext("2d"); width = git_calendar_c.width = document.getElementById("gitcalendarcanvasbox").offsetWidth; height = git_calendar_c.height = 9 * 0.96 * git_calendar_c.width / git_data.length; retinaCanvas(git_calendar_c, git_calendar_ctx, ratio) var linemaxwitdh = height / 9; var lineminwitdh = 0.8 * linemaxwitdh; var setposition = { x: 0.02 * width, y: 0.025 * width }; for (var week in git_data) { weekdata = git_data[week]; for (var day in weekdata) { var dataitem = { date: "", count: "", x: 0, y: 0 }; git_positionplusdata.push(dataitem); git_calendar_ctx.fillStyle = git_thiscolor(git_color, weekdata[day].count); setposition.y = Math.round(setposition.y * 100) / 100; dataitem.date = weekdata[day].date; dataitem.count = weekdata[day].count; dataitem.x = setposition.x; dataitem.y = setposition.y; git_calendar_ctx.fillRect(setposition.x, setposition.y, lineminwitdh, lineminwitdh); setposition.y = setposition.y + linemaxwitdh } setposition.y = 0.025 * width; setposition.x = setposition.x + linemaxwitdh; } if (document.body.clientWidth > 700) { git_calendar_ctx.font = "600 Arial"; git_calendar_ctx.fillStyle = '#aaa'; git_calendar_ctx.fillText("日", 0, 1.9 * linemaxwitdh); git_calendar_ctx.fillText("二", 0, 3.9 * linemaxwitdh); git_calendar_ctx.fillText("四", 0, 5.9 * linemaxwitdh); git_calendar_ctx.fillText("六", 0, 7.9 * linemaxwitdh); var monthindexlist = git_calendar_c.width / 24; for (var index in git_monthchange) { git_calendar_ctx.fillText(git_monthchange[index], monthindexlist, 0.7 * linemaxwitdh); monthindexlist = monthindexlist + git_calendar_c.width / 12 } } git_calendar_c.onmousemove = function (event) { if (document.querySelector('.gitmessage')) { git_tooltip_container.innerHTML = "" } getMousePos(git_calendar_c, event) }; git_tooltip_container.onmousemove = function (event) { if (document.querySelector('.gitmessage')) { git_tooltip_container.innerHTML = "" } }; var getMousePos = (canvas, event) => { var rect = canvas.getBoundingClientRect(); var x = event.clientX - rect.left * (canvas.width / rect.width); var y = event.clientY - rect.top * (canvas.height / rect.height); for (var item of git_positionplusdata) { var lenthx = x - item.x; var lenthy = y - item.y; if (0 < lenthx && lenthx < lineminwitdh) { if (0 < lenthy && lenthy < lineminwitdh) { git_span1 = item.date; git_span2 = item.count; git_x = event.clientX - 100; git_y = event.clientY - 60; html = tooltip_html(git_x, git_y, git_span1, git_span2); append_div_gitcalendar(git_tooltip_container, html) } } } } } } var addlastmonth = () => { if (git_thisdayindex === 0) { thisweekcore(52); thisweekcore(51); thisweekcore(50); thisweekcore(49); thisweekcore(48); git_thisweekdatacore += git_firstdate[6].count; git_amonthago = git_firstdate[6].date } else { thisweekcore(52); thisweekcore(51); thisweekcore(50); thisweekcore(49); thisweek2core(); git_amonthago = git_first2date[git_thisdayindex - 1].date } } var thisweek2core = () => { for (var i = git_thisdayindex - 1; i < git_first2date.length; i++) { git_thisweekdatacore += git_first2date[i].count } } var thisweekcore = (index) => { for (var item of git_data[index]) { git_thisweekdatacore += item.count } } var addlastweek = () => { for (var item of git_lastweek) { git_weekdatacore += item.count } } var addbeforeweek = () => { for (var i = git_thisdayindex; i < git_beforeweek.length; i++) { git_weekdatacore += git_beforeweek[i].count } } var addweek = (data) => { if (git_thisdayindex === 6) { git_aweekago = git_lastweek[0].date; addlastweek() } else { lastweek = data.contributions[51]; git_aweekago = lastweek[git_thisdayindex + 1].date; addlastweek(); addbeforeweek() } } fetch(git_gitapiurl).then(data => data.json()).then(data => { if (document.getElementById('git_loading')) { document.getElementById('git_loading').remove() }; git_data = data.contributions; git_total = data.total; git_first2date = git_data[48]; git_firstdate = git_data[47]; git_firstweek = data.contributions[0]; git_lastweek = data.contributions[52]; git_beforeweek = data.contributions[51]; git_thisdayindex = git_lastweek.length - 1; git_thisday = git_lastweek[git_thisdayindex].date; git_oneyearbeforeday = git_firstweek[0].date; git_monthindex = git_thisday.substring(5, 7) * 1; git_montharrbefore = git_month.splice(git_monthindex, 12 - git_monthindex); git_monthchange = git_montharrbefore.concat(git_month); addweek(data); addlastmonth(); var html = git_main_box(git_monthchange, git_data, git_user, git_color, git_total, git_thisweekdatacore, git_weekdatacore, git_oneyearbeforeday, git_thisday, git_aweekago, git_amonthago); append_div_gitcalendar(git_container, html); responsiveChart() }).catch(function (error) { console.log(error) }); window.onresize = function () { responsiveChart() }; window.onscroll = function () { if (document.querySelector('.gitmessage')) { git_tooltip_container.innerHTML = "" } }; var git_thiscolor = (color, x) => { if (x === 0) { var i = parseInt(x / 2); return color[0] } else if (x < 2) { return color[1] } else if (x < 20) { var i = parseInt(x / 2); return color[i] } else { return color[9] } }; var tooltip_html = (x, y, span1, span2) => { var html = ''; html += `<div class="gitmessage" style="top:${y}px;left: ${x}px;position: fixed;z-index:9999"> <div class="angle-wrapper" style="display:block;"> <span>${span1} </span> <span>${span2}次上传</span> </div> </div>`; return html }; var git_canvas_box = () => { var html = `<div id="gitcalendarcanvasbox"> <canvas id="gitcanvas" style="animation: none;"> </canvas> </div>`; return html }; var git_info_box = (user, color) => { var html = ''; html += `<div id="git_tooltip_container"></div> <div class="contrib-footer clearfix mt-1 mx-3 px-3 pb-1"> <div class="float-left text-gray">数据来源 <a href="https://github.com/${user}" target="blank">@${user}</a> </div> <div class="contrib-legend text-gray">Less <ul class="legend"> <li style="background-color:${color[0]}"></li> <li style="background-color:${color[2]}"></li> <li style="background-color:${color[4]}"></li> <li style="background-color:${color[6]}"></li> <li style="background-color:${color[8]}"></li> </ul>More </div> </div>`; return html }; var git_main_box = (monthchange, git_data, user, color, total, thisweekdatacore, weekdatacore, oneyearbeforeday, thisday, aweekago, amonthago) => { var html = ''; var canvasbox = git_canvas_box(); var infobox = git_info_box(user, color); html += `<div class="position-relative"> <div class="border py-2 graph-before-activity-overview"> <div class="js-gitcalendar-graph mx-md-2 mx-3 d-flex flex-column flex-items-end flex-xl-items-center overflow-hidden pt-1 is-graph-loading graph-canvas gitcalendar-graph height-full text-center"> ${canvasbox} </div> ${infobox} </div> </div>`; html += `<div style="display:flex;width:100%"> <div class="contrib-column contrib-column-first table-column"> <span class="text-muted">过去一年提交</span> <span class="contrib-number">${total}</span> <span class="text-muted">${oneyearbeforeday} - ${thisday}</span> </div> <div class="contrib-column table-column"> <span class="text-muted">最近一月提交</span> <span class="contrib-number">${thisweekdatacore}</span> <span class="text-muted">${amonthago} - ${thisday}</span> </div> <div class="contrib-column table-column"> <span class="text-muted">最近一周提交</span> <span class="contrib-number">${weekdatacore}</span> <span class="text-muted">${aweekago} - ${thisday}</span> </div> </div>`; return html }; }; var append_div_gitcalendar = (parent, text) => { if (typeof text === 'string') { var temp = document.createElement('div'); temp.innerHTML = text; var frag = document.createDocumentFragment(); while (temp.firstChild) { frag.appendChild(temp.firstChild) } parent.appendChild(frag) } else { parent.appendChild(text) } }; var git_container = document.getElementById('git_container'); var git_loading = document.getElementById('git_loading'); git_canlendar(git_user, git_gitapiurl, git_color) }}]]></content>
</entry>
<entry>
<title>标签</title>
<link href="/tags/index.html"/>
<url>/tags/index.html</url>
<content type="html"><![CDATA[]]></content>
</entry>
<entry>
<title></title>
<link href="/js/runtime/runtime.js"/>
<url>/js/runtime/runtime.js</url>
<content type="html"><![CDATA[var now = new Date();function createtime() { var grt = new Date("09/01/2022 00:00:00"); now.setTime(now.getTime() + 250); var days = (now - grt) / 1e3 / 60 / 60 / 24, dnum = Math.floor(days), hours = (now - grt) / 1e3 / 60 / 60 - 24 * dnum, hnum = Math.floor(hours); 1 == String(hnum).length && (hnum = "0" + hnum); var minutes = (now - grt) / 1e3 / 60 - 1440 * dnum - 60 * hnum, mnum = Math.floor(minutes); 1 == String(mnum).length && (mnum = "0" + mnum); var seconds = (now - grt) / 1e3 - 86400 * dnum - 3600 * hnum - 60 * mnum, snum = Math.round(seconds); 1 == String(snum).length && (snum = "0" + snum); let currentTimeHtml = ""; (currentTimeHtml = hnum < 18 && hnum >= 9 ? `<img style="width: 35px;height: 35px;" class='boardsign' src='https://gcore.jsdelivr.net/gh/Alleyway-boop/Figure_bed/image/天气icon_晴天_白天.svg' title='距离大佬也就还差一个大佬~'><span class='textTip'> <br> 本站居然运行了 ${dnum} 天</span><span id='runtime'> ${hnum} 小时 ${mnum} 分 ${snum} 秒 </span> <i class='fas fa-heartbeat' style='color:red'></i>` : `<img style="width: 35px;height: 35px;" class='boardsign' src='https://gcore.jsdelivr.net/gh/Alleyway-boop/Figure_bed/image/dark,夜间模式,黑夜模式,深色模式,暗黑模式.svg' title='夜晚了就该开开心心的玩耍，嘿嘿~'><span class='textTip'> <br> 本站居然运行了 ${dnum} 天</span><span id='runtime'> ${hnum} 小时 ${mnum} 分 ${snum} 秒 </span> <i class='fas fa-heartbeat' style='color:red'></i>`), document.getElementById("workboard") && (document.getElementById("workboard").innerHTML = currentTimeHtml);}setInterval(() => { createtime();}, 250);]]></content>
</entry>
<entry>
<title></title>
<link href="/js/runtime/runtime.min.js"/>
<url>/js/runtime/runtime.min.js</url>
<content type="html"><![CDATA[function createtime(){var e=new Date("09/01/2022 00:00:00");now.setTime(now.getTime()+250);var t=(now-e)/1e3/60/60/24,a=Math.floor(t),r=(now-e)/1e3/60/60-24*a,n=Math.floor(r);1==String(n).length&&(n="0"+n);var s=(now-e)/1e3/60-1440*a-60*n,i=Math.floor(s);1==String(i).length&&(i="0"+i);var o=(now-e)/1e3-86400*a-3600*n-60*i,l=Math.round(o);1==String(l).length&&(l="0"+l);let g="";g=n<18&&n>=9?`<img style="width: 35px;height: 35px;" class='boardsign' src='https://gcore.jsdelivr.net/gh/Alleyway-boop/Figure_bed/image/天气icon_晴天_白天.svg' title='距离大佬也就还差一个大佬~'><span class='textTip'> <br> 本站居然运行了 ${a} 天</span><span id='runtime'> ${n} 小时 ${i} 分 ${l} 秒 </span> <i class='fas fa-heartbeat' style='color:red'></i>`:`<img style="width: 35px;height: 35px;" class='boardsign' src='https://gcore.jsdelivr.net/gh/Alleyway-boop/Figure_bed/image/dark,夜间模式,黑夜模式,深色模式,暗黑模式.svg' title='夜晚了就该开开心心的玩耍，嘿嘿~'><span class='textTip'> <br> 本站居然运行了 ${a} 天</span><span id='runtime'> ${n} 小时 ${i} 分 ${l} 秒 </span> <i class='fas fa-heartbeat' style='color:red'></i>`,document.getElementById("workboard")&&(document.getElementById("workboard").innerHTML=g)}var now=new Date;setInterval(()=>{createtime()},250);]]></content>
</entry>
<entry>
<title></title>
<link href="/js/ali_font.js"/>
<url>/js/ali_font.js</url>
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