数据库SQL去重，保留一条数据

利用SQL,删除掉重复多余的数据，并且只保留一条数据。

1、查找表中多余的重复记录，重复记录是根据单个字段（teamId）来判断

select * from team where teamId in (select teamId from team group by teamId having count(teamId) > 1)

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

teamName in(select teamName from team group by teamName having count(teamName) > 1)

and teamId not in (select min(teamId) from team group by teamName having count(teamName)>1)

1、查找表中多余的重复记录（多个字段）
select * from team t
where (t.teamId,t.teamOrg) in (select teamId,teamOrg from team group by teamId,teamOrg having count(*) > 1)

2、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 team t
where (t.teamId,t.teamOrg) in (select teamId,teamOrg from team group by teamId,teamOrg having count(*) > 1)
and rowid not in (select min(rowid) from team group by teamId,teamOrg having count(*)>1)

3、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 team t
where (t.teamId,t.teamOrg) in (select teamId,teamOrg from team group by teamId ,t.teamOrg having count(*) > 1)

and rowid not in (select min(rowid) from team group by teamId,teamOrg having count(*)>1)   

1.消除一个字段的左边的第一位：

update tableName set [Title]=Right([Title],(len([Title])-1)) where Title like '村%'

2.消除一个字段的右边的第一位：

update tableName set [Title]=left([Title],(len([Title])-1)) where Title like '%村'

1.假删除表中多余的重复记录（多个字段），不包含rowid最小的记录
update team set ispass=-1
where teamId in (select teamId from team group by teamId

1.oracle中利用rowId去删除多余的数据：

(1).在oracle中，每一条记录都有一个rowid，rowid在整个数据库中是唯一的，rowid确定了每条记录是在Oracle中的哪一个数据文件、块、行上。

 

(2).在重复的记录中，可能所有列的内容都相同，但rowid不会相同，所以只要确定出重复记录中那些具有最大rowid的就可以了，其余全部删除。

delete from team where teamName in

(select* from team t where rowid=(select max(rowid) from team where teamName=t.teamName))