mysql 的delete from 子查询限制

1.使用mysql进行delete from操作时，若子查询的 FROM 字句和更新/删除对象使用同一张表，会出现错误。

mysql> DELETE FROM tab1 WHERE col1 = ( SELECT MAX( col1 ) FROM tab1 );
ERROR 1093 (HY000): You can’t specify target table ‘tab1′ for update in FROM clause

针对“同一张表”这个限制，撇开效率不谈，多数情况下都可以通过多加一层select 别名表来变通解决，像这样

DELETE FROM tab1
WHERE col1 = (
SELECT MAX( col1 )
FROM (
SELECT * FROM tab1
) AS t
);


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2. mysql delete from where in 时后面 的查询语句里不能加where条件


Sql代码
      delete from `t_goods` where fi_id in (select * from ( select fi_id from `t_goods` where fs_num is null and fs_name is null and fs_type is null and fs_using is null and fs_lifetime is null) b) 


Sql代码
      delete from `t_goods` where fi_id in (select fi_id from `t_goods` where fs_num is null and fs_name is null and fs_type is null and fs_using is null and fs_lifetime is null)  


Sql代码
      delete from `t_goods` where fi_id in ( select fi_id from `t_goods` )  

上面三种情况，只有中间的不能执行。

综合起来就是mysql delete from where in 时后面 的查询语句里不能加where条件

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3. delete from table... 这其中table不能使用别名

Sql代码

    delete from student a where a.id in (1,2);(执行失败)

   

     select a.* from student a where a.id in (1,2);(执行成功)