转载地址：https://blog.csdn.net/anya/article/details/6407280/
用SQL语句,删除掉重复项只保留一条
在几千条记录里,存在着些相同的记录,如何能用SQL语句,删除掉重复的呢
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 countpeopleId) > 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 peopleName in select peopleName from people group by peopleName having countpeopleName) > 1)
and peopleId not in select minpeopleId) from people group by peopleName having countpeopleName)>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 minrowid) 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 minrowid) from vitae group by peopleId,seq having count*)>1)
6.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%’
7.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’
8.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 vitae set ispass=-1
where peopleId in select peopleId from vitae group by peopleId
eg：select * from payrecdb.dt_strongrelation x
where x.payOrRelUserID ,x.rcvOrRelUserID) in select payOrRelUserID,rcvOrRelUserID from payrecdb.dt_strongrelation group by payOrRelUserID,rcvOrRelUserID having count*) > 1)