1093

目的：查询一张表的相同的两条数据，并删除一条数据。

分析 先查询出相同的数据，然后删除

查询相同的数据 

SELECT a.id FROM account a GROUP BY a.username HAVING COUNT(a.username)>1；

DELETE FROM account WHERE id = (SELECT a.id FROM account a GROUP BY a.username HAVING COUNT(a.username)>1) ；

1093 - You can't specify target table 'account' for update in FROM clause

不能为FROM子句中的更新指定目标表'account'。

修改后：

DELETE FROM account WHERE id = 

(SELECT t.id from

(SELECT a.id FROM account a GROUP BY a.username HAVING COUNT(a.username)>1) t
)；