Mysql更新数据时，报 “You can't specify target table 'message ' for update in FROM clause” 解决办法

Posted 2022-09-01 testeyes

报错的SQL为：

delete from message where id not in  (select min(id) as id from message group by content); 

 

报错信息的中文意思为：不能在FROM子句中更新  message表数据，原因是 "不能在从本表中查出数据范围后，然后直接更新本表"，

解决方法思路是，让数据库认为，你查出的数据范围，是不从本表中查出来的，实现步骤如下：

1、用as，给查出的数据表，设置别名为a，即 （select min(id) as id from message group by content）as a

2、用别名，查出数据范围，即 select a.id from (select min(id) as id from message group by content）as a

 

修改后的完整SQL为

delete from message where id not in  (select a.id from (select min(id) as id from message group by content) as a);