Id name age salary
1 yzk 80 1000
2 yzk 80 2000
3 tom 20 20000
4 tom 20 20000
5 im 20 20000
使用Distinct 去重:
SELECT DISTINCT Name FROM Persons（Distinct 只能去除结果集中一模一样的数据）
获取不重复数据1：
SELECT Name, age FROM Persons GROUP BY Name, Gender
获取不重复数据2：
SELECT MAX(Id) AS Expr1, Name, Gender FROM Persons GROUP BY Name, age
获取不重复数据：
select * from Persons where Id in ( SELECT MAX(Id) AS Expr1 FROM Persons GROUP BY Name, age )
删除重复的数据：
delete from Persons where Id not in ( SELECT MAX(Id) AS Expr1 FROM Persons GROUP BY Name, age )