前言

最近对数据库进行复习这篇文章也只是记录一些遇到到问题，并记录解决方法。

查找表(Demo)中多余的重复记录，重复记录是根据单个字段（name）来判断

select * from Demo01 where name in 
(select name from Demo group by name having count(name) > 1);

删除表(Demo)中多余的重复记录，重复记录是根据单个字段（name）来判断，只留有id最小的记录

delete from Demo where 
name in (select name from Demo group by name   having count(name) > 1) and 
id not in (select min(id) from Demo group by name having count(name )>1);

查找表(Demo)中多余的重复记录（多个字段 ）

select * from Demo a where
(a.name,a.age) in
(select name,age from Demo group by name,age having count(*) > 1);

查找表(Demo)中多余的重复记录（多个字段），不包含id最小的记录

select * from Demo a where 
(a.name,a.age) in (select name,age from Demo group by 
name,age having count(*) > 1) and
id not in (select min(id) from Demo group by name,age having count(*)>1);

仅供参考，希望自己的分享帮助有需要的人。