SQL删除与JOIN另一个表的WHERE条件

我必须删除guide_category中与guide表（死关系） guide_category行。

这是我想要做的，但它当然不起作用。

 DELETE FROM guide_category AS pgc WHERE pgc.id_guide_category IN (SELECT id_guide_category FROM guide_category AS gc LEFT JOIN guide AS g ON g.id_guide = gc.id_guide WHERE g.title IS NULL) 

错误：

您无法在FROM子句中指定目标表“guide_category”进行更新

Answer 1

由于locking实现问题， MySQL不允许用DELETE或UPDATE引用受影响的表。

你需要在这里做一个JOIN ：

 DELETE gc.* FROM guide_category AS gc LEFT JOIN guide AS g ON g.id_guide = gc.id_guide WHERE g.title IS NULL 

或者只是使用NOT IN ：

 DELETE FROM guide_category AS gc WHERE id_guide NOT IN ( SELECT id_guide FROM guide ) 

Answer 2

我想，从你的描述来看，以下就足够了：

 DELETE FROM guide_category WHERE id_guide NOT IN (SELECT id_guide FROM guide) 

我认为，在涉及的表格上没有参照完整性约束，是吗？

Answer 3

试试这个示例SQL脚本以便于理解，

 CREATE TABLE TABLE1 (REFNO VARCHAR(10)) CREATE TABLE TABLE2 (REFNO VARCHAR(10)) --TRUNCATE TABLE TABLE1 --TRUNCATE TABLE TABLE2 INSERT INTO TABLE1 SELECT 'TEST_NAME' INSERT INTO TABLE1 SELECT 'KUMAR' INSERT INTO TABLE1 SELECT 'SIVA' INSERT INTO TABLE1 SELECT 'SUSHANT' INSERT INTO TABLE2 SELECT 'KUMAR' INSERT INTO TABLE2 SELECT 'SIVA' INSERT INTO TABLE2 SELECT 'SUSHANT' SELECT * FROM TABLE1 SELECT * FROM TABLE2 DELETE T1 FROM TABLE1 T1 JOIN TABLE2 T2 ON T1.REFNO = T2.REFNO 

你的情况是：

  DELETE pgc FROM guide_category pgc LEFT JOIN guide g ON g.id_guide = gc.id_guide WHERE g.id_guide IS NULL 

Answer 4

怎么样：

 DELETE guide_category WHERE id_guide_category IN ( SELECT id_guide_category FROM guide_category AS gc LEFT JOIN guide AS g ON g.id_guide = gc.id_guide WHERE g.title IS NULL )