diff --git a/expression/builtin_string.go b/expression/builtin_string.go
index d07536c42bee5..749d3453d0775 100644
--- a/expression/builtin_string.go
+++ b/expression/builtin_string.go
@@ -180,6 +180,11 @@ func SetBinFlagOrBinStr(argTp *types.FieldType, resTp *types.FieldType) {
 	}
 }
 
+// addBinFlag add the binary flag to `tp` if its charset is binary
+func addBinFlag(tp *types.FieldType) {
+	SetBinFlagOrBinStr(tp, tp)
+}
+
 type lengthFunctionClass struct {
 	baseFunctionClass
 }
@@ -275,10 +280,10 @@ func (c *concatFunctionClass) getFunction(ctx sessionctx.Context, args []Express
 	if err != nil {
 		return nil, err
 	}
+	addBinFlag(bf.tp)
 	bf.tp.Flen = 0
 	for i := range args {
 		argType := args[i].GetType()
-		SetBinFlagOrBinStr(argType, bf.tp)
 
 		if argType.Flen < 0 {
 			bf.tp.Flen = mysql.MaxBlobWidth
@@ -350,9 +355,9 @@ func (c *concatWSFunctionClass) getFunction(ctx sessionctx.Context, args []Expre
 	}
 	bf.tp.Flen = 0
 
+	addBinFlag(bf.tp)
 	for i := range args {
 		argType := args[i].GetType()
-		SetBinFlagOrBinStr(argType, bf.tp)
 
 		// skip separator param
 		if i != 0 {
@@ -2000,8 +2005,7 @@ func (c *lpadFunctionClass) getFunction(ctx sessionctx.Context, args []Expressio
 		return nil, err
 	}
 	bf.tp.Flen = getFlen4LpadAndRpad(bf.ctx, args[1])
-	SetBinFlagOrBinStr(args[0].GetType(), bf.tp)
-	SetBinFlagOrBinStr(args[2].GetType(), bf.tp)
+	addBinFlag(bf.tp)
 
 	valStr, _ := ctx.GetSessionVars().GetSystemVar(variable.MaxAllowedPacket)
 	maxAllowedPacket, err := strconv.ParseUint(valStr, 10, 64)
@@ -2133,8 +2137,7 @@ func (c *rpadFunctionClass) getFunction(ctx sessionctx.Context, args []Expressio
 		return nil, err
 	}
 	bf.tp.Flen = getFlen4LpadAndRpad(bf.ctx, args[1])
-	SetBinFlagOrBinStr(args[0].GetType(), bf.tp)
-	SetBinFlagOrBinStr(args[2].GetType(), bf.tp)
+	addBinFlag(bf.tp)
 
 	valStr, _ := ctx.GetSessionVars().GetSystemVar(variable.MaxAllowedPacket)
 	maxAllowedPacket, err := strconv.ParseUint(valStr, 10, 64)
@@ -2668,9 +2671,7 @@ func (c *makeSetFunctionClass) getFunction(ctx sessionctx.Context, args []Expres
 	if err != nil {
 		return nil, err
 	}
-	for i, length := 0, len(args); i < length; i++ {
-		SetBinFlagOrBinStr(args[i].GetType(), bf.tp)
-	}
+	addBinFlag(bf.tp)
 	bf.tp.Flen = c.getFlen(bf.ctx, args)
 	if bf.tp.Flen > mysql.MaxBlobWidth {
 		bf.tp.Flen = mysql.MaxBlobWidth
@@ -3589,8 +3590,7 @@ func (c *insertFunctionClass) getFunction(ctx sessionctx.Context, args []Express
 		return nil, err
 	}
 	bf.tp.Flen = mysql.MaxBlobWidth
-	SetBinFlagOrBinStr(args[0].GetType(), bf.tp)
-	SetBinFlagOrBinStr(args[3].GetType(), bf.tp)
+	addBinFlag(bf.tp)
 
 	valStr, _ := ctx.GetSessionVars().GetSystemVar(variable.MaxAllowedPacket)
 	maxAllowedPacket, err := strconv.ParseUint(valStr, 10, 64)
diff --git a/expression/typeinfer_test.go b/expression/typeinfer_test.go
index 8a46b32664c24..d1d5d83210d48 100644
--- a/expression/typeinfer_test.go
+++ b/expression/typeinfer_test.go
@@ -240,8 +240,14 @@ func (s *testInferTypeSuite) createTestCase4StrFuncs() []typeInferTestCase {
 		{"strcmp(c_char, c_char)", mysql.TypeLonglong, charset.CharsetBin, mysql.BinaryFlag, 2, 0},
 		{"space(c_int_d)", mysql.TypeLongBlob, mysql.DefaultCharset, 0, mysql.MaxBlobWidth, types.UnspecifiedLength},
 		{"CONCAT(c_binary, c_int_d)", mysql.TypeVarString, charset.CharsetBin, mysql.BinaryFlag, 40, types.UnspecifiedLength},
+<<<<<<< HEAD
 		{"CONCAT(c_bchar, c_int_d)", mysql.TypeVarString, charset.CharsetUTF8MB4, mysql.BinaryFlag, 40, types.UnspecifiedLength},
 		{"CONCAT('T', 'i', 'DB')", mysql.TypeVarString, charset.CharsetUTF8MB4, 0, 4, types.UnspecifiedLength},
+=======
+		{"CONCAT(c_bchar, c_int_d)", mysql.TypeVarString, charset.CharsetUTF8MB4, 0, 40, types.UnspecifiedLength},
+		{"CONCAT(c_bchar, 0x80)", mysql.TypeVarString, charset.CharsetUTF8MB4, 0, 23, types.UnspecifiedLength},
+		{"CONCAT('T', 'i', 'DB')", mysql.TypeVarString, charset.CharsetUTF8MB4, 0 | mysql.NotNullFlag, 4, types.UnspecifiedLength},
+>>>>>>> 7229416ba... functions: fix some string function has wrong collation and flag (#23835)
 		{"CONCAT('T', 'i', 'DB', c_binary)", mysql.TypeVarString, charset.CharsetBin, mysql.BinaryFlag, 24, types.UnspecifiedLength},
 		{"CONCAT_WS('-', 'T', 'i', 'DB')", mysql.TypeVarString, charset.CharsetUTF8MB4, 0, 6, types.UnspecifiedLength},
 		{"CONCAT_WS(',', 'TiDB', c_binary)", mysql.TypeVarString, charset.CharsetBin, mysql.BinaryFlag, 25, types.UnspecifiedLength},
@@ -451,8 +457,9 @@ func (s *testInferTypeSuite) createTestCase4StrFuncs() []typeInferTestCase {
 		{"find_in_set(c_set        , c_text_d)", mysql.TypeLonglong, charset.CharsetBin, mysql.BinaryFlag, 3, 0},
 		{"find_in_set(c_enum       , c_text_d)", mysql.TypeLonglong, charset.CharsetBin, mysql.BinaryFlag, 3, 0},
 
-		{"make_set(c_int_d      , c_text_d)", mysql.TypeVarString, charset.CharsetUTF8MB4, mysql.BinaryFlag, 65535, types.UnspecifiedLength},
+		{"make_set(c_int_d      , c_text_d)", mysql.TypeVarString, charset.CharsetUTF8MB4, 0, 65535, types.UnspecifiedLength},
 		{"make_set(c_bigint_d   , c_text_d, c_binary)", mysql.TypeMediumBlob, charset.CharsetBin, mysql.BinaryFlag, 65556, types.UnspecifiedLength},
+		{"make_set(1   , c_text_d, 0x40)", mysql.TypeVarString, charset.CharsetUTF8MB4, 0, 65535, types.UnspecifiedLength},
 
 		{"quote(c_int_d      )", mysql.TypeVarString, charset.CharsetUTF8MB4, 0, 42, types.UnspecifiedLength},
 		{"quote(c_bigint_d   )", mysql.TypeVarString, charset.CharsetUTF8MB4, 0, 42, types.UnspecifiedLength},
@@ -465,6 +472,7 @@ func (s *testInferTypeSuite) createTestCase4StrFuncs() []typeInferTestCase {
 		{"convert(c_text_d using 'binary')", mysql.TypeLongBlob, charset.CharsetBin, mysql.BinaryFlag, mysql.MaxBlobWidth, types.UnspecifiedLength},
 
 		{"insert(c_varchar, c_int_d, c_int_d, c_varchar)", mysql.TypeLongBlob, charset.CharsetUTF8MB4, 0, mysql.MaxBlobWidth, types.UnspecifiedLength},
+		{"insert(c_varchar, c_int_d, c_int_d, 0x40)", mysql.TypeLongBlob, charset.CharsetUTF8MB4, 0, mysql.MaxBlobWidth, types.UnspecifiedLength},
 		{"insert(c_varchar, c_int_d, c_int_d, c_binary)", mysql.TypeLongBlob, charset.CharsetBin, mysql.BinaryFlag, mysql.MaxBlobWidth, types.UnspecifiedLength},
 		{"insert(c_binary, c_int_d, c_int_d, c_varchar)", mysql.TypeLongBlob, charset.CharsetBin, mysql.BinaryFlag, mysql.MaxBlobWidth, types.UnspecifiedLength},
 		{"insert(c_binary, c_int_d, c_int_d, c_binary)", mysql.TypeLongBlob, charset.CharsetBin, mysql.BinaryFlag, mysql.MaxBlobWidth, types.UnspecifiedLength},