2010.09.10——— sql 去除重复数据
2010.09.10——— sql 去除重复数据

参考

http://blog.csdn.net/an410398183/archive/2009/10/11/4654864.aspx

--功能概述:删除重复记录
1、查找表中多余的重复记录，重复记录是根据单个字段（peopleId）来判断

select * from people where peopleId in (select  peopleId  from  people  group  by  peopleId  having  count(peopleId) > 1) 

2、删除表中多余的重复记录，重复记录是根据单个字段（peopleId）来判断，只留有rowid最小的记录

delete from people where peopleId  in (select  peopleId  from people  group  by  peopleId  having  count(peopleId) > 1) and rowid not in (select min(rowid) from  people  group by peopleId  having count(peopleId )>1)

3、查找表中多余的重复记录（多个字段）

select * from vitae a where (a.peopleId,a.seq) in  (select peopleId,seq from vitae group by peopleId,seq  having count(*) > 1)

4、删除表中多余的重复记录（多个字段），只留有rowid最小的记录

delete from vitae a where (a.peopleId,a.seq) in  (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1) and rowid not in (select min(rowid) from vitae group by peopleId,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

select * from vitae a where (a.peopleId,a.seq) in  (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1) and rowid not in (select min(rowid) from vitae group by peopleId,seq having count(*)>1) 

比方说在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，
现在就是需要查询出在该表中的各记录之间，“name”值存在重复的项；
Select Name,Count(*) From A Group By Name Having Count(*) > 1

如果还查性别也相同大则如下:

Select Name,sex,Count(*) From A Group By Name,sex Having Count(*) > 1 --方法1：select a.* from tb a where val = (select min(val) from tb where name = a.name) order by a.name--方法2：select a.* from tb a where not exists(select 1 from tb where name = a.name and val < a.val)--方法3：select a.* from tb a,(select name,min(val) val from tb group by name) b where a.name = b.name and a.val = b.val order by a.name--方法4：select a.* from tb a inner join (select name , min(val) val from tb group by name) b on a.name = b.name and a.val = b.val order by a.name--方法5select a.* from tb a where 1 > (select count(*) from tb where name = a.name and val < a.val) order by