SQL DELETE与JOIN另一个表在WHERE条件

Question

我必须从中删除guide_category与guide表无关的行（无效关系）。

这是我想做的，但是它当然不起作用。

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：

您不能在FROM子句中指定目标表’guide_category’进行更新

Answer 1

由于锁定实现问题，MySQL不允许使用DELETE或引用受影响的表UPDATE。

您需要在JOIN此处制作一个：

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

或只是使用NOT IN：

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