SQL DELETE与JOIN另一个表在WHERE条件 [英] SQL DELETE with JOIN another table for WHERE condition

问题描述

我必须从guide_category中删除与guide表没有任何关系(死关系)的行.

I have to delete rows from guide_category that have no relation with guide table (dead relations).

这是我想要做的，但是它当然不起作用.

Here is what I want to do, but it of course does not work.

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

You can't specify target table 'guide_category' for update in FROM clause

推荐答案

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

Due to the locking implementation issues, MySQL does not allow referencing the affected table with DELETE or UPDATE.

您需要在此处输入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

或仅使用NOT IN:

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

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