mysql修改删除You can't specify target table for update in FROM clause的问题

Posted 2021-02-10 淡淡人生过

表中出现重复数据，需要删除重复数据，只保留一条

DELETE 
FROM
    crm_participant 
WHERE
    id IN (

SELECT
    c.id cid 
FROM
    crm_participant c 
WHERE
    c.parentPhone IN ( SELECT a.parentPhone FROM crm_participant a GROUP BY a.parentPhone HAVING count( a.parentPhone ) > 1 ) 
    AND c.id NOT IN ( SELECT min( b.id ) FROM crm_participant b GROUP BY b.parentPhone HAVING count( b.parentPhone ) > 1 ) 
ORDER BY
    c.parentPhone 

    )


错误信息：

> 1093 - You can‘t specify target table ‘crm_participant‘ for update in FROM clause
> 时间: 0.005s

　　

问题分细：
       mysql不允许对同一个表中查出来的数据作为条件，在执行跟新操作。 在一条 sql 语句中不能先查出来部分内容，再同时又对当前表作修改。
       

 

解决办法：这个是正确的sql,其实就是对上边的红色部分的查询sql进行了一层包裹。让查询出来的信息被一个  select 包裹一下，然后作为条件就可以了

DELETE 
FROM
    crm_participant 
WHERE
    id IN (
SELECT
    v.cid 
FROM
    (
SELECT
    c.id cid 
FROM
    crm_participant c 
WHERE
    c.parentPhone IN ( SELECT a.parentPhone FROM crm_participant a GROUP BY a.parentPhone HAVING count( a.parentPhone ) > 1 ) 
    AND c.id NOT IN ( SELECT min( b.id ) FROM crm_participant b GROUP BY b.parentPhone HAVING count( b.parentPhone ) > 1 ) 
ORDER BY
    c.parentPhone 
    ) v 
     )