Update 0512. Game Play Analysis II.sql

haibarawu · Jun 9, 2020 · 0c830c6 · 0c830c6
1 parent f840e19
commit 0c830c6
Showing 1 changed file with 30 additions and 2 deletions.
diff --git a/Database/0512. Game Play Analysis II.sql b/Database/0512. Game Play Analysis II.sql
@@ -1,4 +1,4 @@
-/********************************************************************************
+/****************************************************************************************************
 512. Game Play Analysis II
 
 Difficulty: Easy
@@ -15,7 +15,12 @@ Table: Activity
 (player_id, event_date) is the primary key of this table.
 This table shows the activity of players of some game.
 Each row is a record of a player who logged in and played a number of games (possibly 0) before logging out on some day using some device.
+表的主键是 (player_id, event_date)。
+这张表展示了一些游戏玩家在游戏平台上的行为活动。
+每行数据记录了一名玩家在退出平台之前，当天使用同一台设备登录平台后打开的游戏的数目（可能是 0 个）。
+
 Write a SQL query that reports the device that is first logged in for each player.
+描述每一个玩家首次登陆的设备名称
 
 The query result format is in the following example:
 
@@ -38,9 +43,17 @@ Result table:
 | 2         | 3         |
 | 3         | 1         |
 +-----------+-----------+
-********************************************************************************/
+****************************************************************************************************/
+
 
+/****************************************************************************************************
+解题思路：
+在 511 题中已经得到了用户第一次登录的时间 query01。
+只需要 query01 与原始表 Activity 相关联，使 用户ID 和 登录时间 匹配，即可得到第一次登录平台使用的设备 device_id。
+****************************************************************************************************/
 
+
+--Method01:
 SELECT DISTINCT player_id, device_id
 FROM Activity
 WHERE (player_id, event_date) IN (
@@ -49,3 +62,18 @@ WHERE (player_id, event_date) IN (
   GROUP BY player_id
 )
 
+
+/****************************************************************************************************/
+
+
+--Method02:
+SELECT a.player_id, a.device_id
+FROM Activity AS a,
+(	SELECT b.player_id, MIN(b.event_date) AS first_login
+	FROM Activity AS b
+	GROUP BY b.player_id
+) AS f
+WHERE a.player_id = f.player_id
+AND a.event_date = f.first_login
+
+