mysql查询表内重复记录方法示例。
1、查找表中多余的重复记录，重复记录是根据单个字段（myinfoId）来判断
复制代码 代码示例:
select * from myinfo
where myinfoId in (select myinfoId from myinfo group by myinfoId having count(myinfoId) > 1)
2、删除表中多余的重复记录，重复记录是根据单个字段（myinfoId）来判断，只留有一个记录
复制代码 代码示例:
delete from myinfo
where myinfoId in (select myinfoId from myinfo group by myinfoId having count(myinfoId) > 1)
and min(id) not in (select id from myinfo group by myinfoId having count(myinfoId )>1)
3、删除表中多余的重复记录（多个字段），只留有rowid最小的记录
复制代码 代码示例:
delete from vitae a
where (a.myinfoId,a.seq) in (select myinfoId,seq from vitae group by myinfoId,seq having count(*) > 1)
and rowid not in (select min(rowid) from vitae group by myinfoId,seq having count(*)>1)
4、查找表中多余的重复记录（多个字段）
复制代码 代码示例:
select * from vitae a
where (a.myinfoId,a.seq) in (select myinfoId,seq from vitae group by myinfoId,seq having count(*) > 1)
5、查找表中多余的重复记录（多个字段），不包含rowid最小的记录
复制代码 代码示例:
select * from vitae a
where (a.myinfoId,a.seq) in (select myinfoId,seq from vitae group by myinfoId,seq having count(*) > 1)
and rowid not in (select min(rowid) from vitae group by myinfoId,seq having count(*)>1)
例如，在A表中存在一个字段“name”， 而且不同记录之间的“name”值有可能会相同，需要查询出在该表中的各记录之间，“name”值存在重复的项；
复制代码 代码示例:
Select Name,Count(*) From A Group By Name Having Count(*) > 1
查性别，则sql语句为：
复制代码 代码示例:
Select Name,sex,Count(*) From A Group By Name,sex Having Count(*) > 1
