当前位置:编程学习 > asp >>

mysql删除重复数据的方法已经测试过

mysql 查找出重复数据 然后把删除重复的数据 保留一条

delete from temp  where id in (select id from (select  max(id) as id,count(url) as count from temp group by url having count >1 order by count desc) as tab )

如何去掉数据库重复记录并且只保留一条记录

在n条记录里,存在着些相同的记录,如何能用SQL语句,删除掉重复并保留一条呢?方法如下:

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
[sql] view plaincopy
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
[sql] view plaincopy
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) 
[sql] view plaincopy
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
[sql] view plaincopy
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
[sql] view plaincopy
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)  
CopyRight © 2012 站长网 编程知识问答 www.zzzyk.com All Rights Reserved
部份技术文章来自网络,