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 'tab' where id in (select min(id) from tag GROUP BY field1,field2 HAVING COUNT(id)>1);error: You can't specify target table 'tab' for update in FROM clause.(不能为FROM子句中的更新指定目标表'tab')

针对“同一张表”这个限制，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 'tab' where id in(    select id from     (        select max(id) from 'tab' GROUP BY field1,field2 HAVING COUNT(id)>1    ) ids);

2.delete from table... 这其中table不能使用别名

• mysql> delete from table a where a.id in (1,2);(语法错误)
• mysql> select a.* from table a where a.id in (1,2);(执行成功)