SQL报错：You can’t specify target table ‘person’ for update in FROM clause的解决方法

• 报错原因：在MySQL中不能在同一条SQL中查询出一张表的某些值，再直接用这些值更新或删除这张表。
• 解决方案：将查询出的结果用SELECT再查询一次，得到一张额外的临时表，再用临时表的值做更新或删除。

报错语句：

delete from person where id in (select id from (select max(id) as id from person group by email having count(id)>1) a);

解决后：

delete from person where id not in (select id from (select min(id) as id from person group by email) a);