1.取得不重复的数据
select * from Persons where Id in ( SELECT MAX(Id) AS Expr1 FROM Persons GROUP BY Name, Gender )
2.删除重复的数据【MAX换成MIN会有不同的效果】(group by之后数据重复的只会留下一条)
delete from Persons where Id not in ( SELECT MAX(Id) AS Expr1 FROM Persons GROUP BY Name, Gender )