1、

不能先select出同一表中的某些值，再update这个表(在同一语句中)

DELETE FROM Person WHERE id NOT IN 
	( SELECT MIN(id) as id 
		FROM Person GROUP BY email )

所以要通过子表（派生表）

 DELETE FROM Person WHERE id NOT IN
 	 ( select *from (SELECT MIN(id) as id 
 	 FROM Person GROUP BY email ) as a )

**ps:**每个派生表必须有自己的别名,所以给查出的子表一个别名

2、

如果在delete时使用了别名，就要在delete与from中加入别名

delete p1 from person p1,perosn p2 
where p1.id = p2.id;