feat: add EXISTS and NOT EXISTS support

README.ZH_CN.md

@@ -757,6 +757,12 @@ orders, err := o.WithContext(ctx).Where(u.Columns(o.Amount).Gt(o.WithContext(ctx
 subQuery := u.WithContext(ctx).Select(u.Age.Avg()).Where(u.Name.Like("name%"))
 users, err := u.WithContext(ctx).Select(u.Age.Avg().As("avgage")).Group(u.Name).Having(u.Columns(u.Age.Avg()).Gt(subQuery).Find()
 // SELECT AVG(age) as avgage FROM `users` GROUP BY `name` HAVING AVG(age) > (SELECT AVG(age) FROM `users` WHERE name LIKE "name%")
+
+// 找出交易数量在100和200之间的用户
+subQuery1 := o.WithContext(ctx).Select(o.ID).Where(o.UserID.EqCol(u.ID), o.Amount.Gt(100))
+subQuery2 := o.WithContext(ctx).Select(o.ID).Where(o.UserID.EqCol(u.ID), o.Amount.Gt(200))
+u.WithContext(ctx).Exists(subQuery1).Not(u.WithContext(ctx).Exists(subQuery2)).Find()
+// SELECT * FROM `users` WHERE EXISTS (SELECT `orders`.`id` FROM `orders` WHERE `orders`.`user_id` = `users`.`id` AND `orders`.`amount` > 100 AND `orders`.`deleted_at` IS NULL) AND NOT EXISTS (SELECT `orders`.`id` FROM `orders` WHERE `orders`.`user_id` = `users`.`id` AND `orders`.`amount` > 200 AND `orders`.`deleted_at` IS NULL) AND `users`.`deleted_at` IS NULL
 ```
 
 ###### <span id="from-subquery">From 子查询</span>

README.md

@@ -760,6 +760,12 @@ orders, err := o.WithContext(ctx).Where(u.Columns(o.Amount).Gt(o.WithContext(ctx
 subQuery := u.WithContext(ctx).Select(u.Age.Avg()).Where(u.Name.Like("name%"))
 users, err := u.WithContext(ctx).Select(u.Age.Avg().As("avgage")).Group(u.Name).Having(u.Columns(u.Age.Avg()).Gt(subQuery).Find()
 // SELECT AVG(age) as avgage FROM `users` GROUP BY `name` HAVING AVG(age) > (SELECT AVG(age) FROM `users` WHERE name LIKE "name%")
+
+// Select users with orders between 100 and 200
+subQuery1 := o.WithContext(ctx).Select(o.ID).Where(o.UserID.EqCol(u.ID), o.Amount.Gt(100))
+subQuery2 := o.WithContext(ctx).Select(o.ID).Where(o.UserID.EqCol(u.ID), o.Amount.Gt(200))
+u.WithContext(ctx).Exists(subQuery1).Not(u.WithContext(ctx).Exists(subQuery2)).Find()
+// SELECT * FROM `users` WHERE EXISTS (SELECT `orders`.`id` FROM `orders` WHERE `orders`.`user_id` = `users`.`id` AND `orders`.`amount` > 100 AND `orders`.`deleted_at` IS NULL) AND NOT EXISTS (SELECT `orders`.`id` FROM `orders` WHERE `orders`.`user_id` = `users`.`id` AND `orders`.`amount` > 200 AND `orders`.`deleted_at` IS NULL) AND `users`.`deleted_at` IS NULL
 ```
 
 ###### From SubQuery

field/export.go

@@ -173,15 +173,22 @@ func AssignSubQuery(columns []Expr, subQuery *gorm.DB) AssignExpr {
 type CompareOperate string
 
 const (
-	EqOp  CompareOperate = " = "
-	NeqOp CompareOperate = " <> "
-	GtOp  CompareOperate = " > "
-	GteOp CompareOperate = " >= "
-	LtOp  CompareOperate = " < "
-	LteOp CompareOperate = " <= "
+	EqOp     CompareOperate = " = "
+	NeqOp    CompareOperate = " <> "
+	GtOp     CompareOperate = " > "
+	GteOp    CompareOperate = " >= "
+	LtOp     CompareOperate = " < "
+	LteOp    CompareOperate = " <= "
+	ExistsOp CompareOperate = "EXISTS "
 )
 
 func CompareSubQuery(op CompareOperate, column Expr, subQuery *gorm.DB) Expr {
+	if op == ExistsOp {
+		return expr{e: clause.Expr{
+			SQL:  fmt.Sprint(op, "(?)"),
+			Vars: []interface{}{subQuery},
+		}}
+	}
 	return expr{e: clause.Expr{
 		SQL:  fmt.Sprint("?", op, "(?)"),
 		Vars: []interface{}{column.RawExpr(), subQuery},

internal/template/method.go

@@ -53,6 +53,10 @@ func ({{.S}} {{.NewStructName}}Do) Where(conds ...gen.Condition) *{{.NewStructNa
 	return {{.S}}.withDO({{.S}}.DO.Where(conds...))
 }
 
+func ({{.S}} {{.NewStructName}}Do) Exists(subquery interface{UnderlyingDB() *gorm.DB}) *{{.NewStructName}}Do {
+	return {{.S}}.Where(field.CompareSubQuery(field.ExistsOp, nil, subquery.UnderlyingDB()))
+}
+
 func ({{.S}} {{.NewStructName}}Do) Order(conds ...field.Expr) *{{.NewStructName}}Do {
 	return {{.S}}.withDO({{.S}}.DO.Order(conds...))
 }