New Comma Expression (#4524)

* Add new comma expression

* Add comma expression unit test

clause/select.go

@@ -43,3 +43,17 @@ func (s Select) MergeClause(clause *Clause) {
 		clause.Expression = s
 	}
 }
+
+// CommaExpression represents a group of expressions separated by commas.
+type CommaExpression struct {
+	Exprs []Expression
+}
+
+func (comma CommaExpression) Build(builder Builder) {
+	for idx, expr := range comma.Exprs {
+		if idx > 0 {
+			_, _ = builder.WriteString(", ")
+		}
+		expr.Build(builder)
+	}
+}

clause/select_test.go

@@ -31,6 +31,18 @@ func TestSelect(t *testing.T) {
 			}, clause.From{}},
 			"SELECT `name` FROM `users`", nil,
 		},
+		{
+			[]clause.Interface{clause.Select{
+				Expression: clause.CommaExpression{
+					Exprs: []clause.Expression{
+						clause.NamedExpr{"?", []interface{}{clause.Column{Name: "id"}}},
+						clause.NamedExpr{"?", []interface{}{clause.Column{Name: "name"}}},
+						clause.NamedExpr{"LENGTH(?)", []interface{}{clause.Column{Name: "mobile"}}},
+					},
+				},
+			}, clause.From{}},
+			"SELECT `id`, `name`, LENGTH(`mobile`) FROM `users`", nil,
+		},
 	}
 
 	for idx, result := range results {