Oracle 删除重复数据只留一条
查询及删除重复记录的SQL语句
转自： http://www.cnblogs.com/252e/archive/2012/09/13/2682817.html
1、查找表中多余的重复记录，重复记录是根据单个字段（Id）来判断
select * from 表 where Id in (select Id from 表 group byId having count(Id) > 1)
2、删除表中多余的重复记录，重复记录是根据单个字段（Id）来判断，只留有rowid最小的记录
DELETE from 表 WHERE (id) IN ( SELECT id FROM 表 GROUP BY id HAVING COUNT(id) > 1) AND ROWID NOT IN (SELECT MIN(ROWID) FROM 表 GROUP BY id HAVING COUNT(*) > 1);
3、查找表中多余的重复记录（多个字段）
select * from 表 a where (a.Id,a.seq) in(select Id,seq from 表 group by Id,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 表 a where (a.Id,a.seq) in (select Id,seq from 表 group by Id,seq having count(*) > 1) and rowid not in (select min(rowid) from 表 group by Id,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 表 a where (a.Id,a.seq) in (select Id,seq from 表 group by Id,seq having count(*) > 1) and rowid not in (select min(rowid) from 表 group by Id,seq having count(*)>1)
例如：
服务关系表， SERVICE_ID RELATE_ID RELATE_TYPE 三个合起来作主键，由于最初表没有建主键存在重复数据.
select * from ops_service_relate a where (a.SERVICE_ID,a.RELATE_ID,a.RELATE_TYPE) in (select SERVICE_ID,RELATE_ID,RELATE_TYPE from ops_service_relate group by SERVICE_ID,RELATE_ID,RELATE_TYPE having count(*) > 1) and rowid not in (select min(rowid) from ops_service_relate group by SERVICE_ID,RELATE_ID,RELATE_TYPE having count(*)>1)
delete from ops_service_relate a where (a.SERVICE_ID,a.RELATE_ID,a.RELATE_TYPE) in (select SERVICE_ID,RELATE_ID,RELATE_TYPE from ops_service_relate group by SERVICE_ID,RELATE_ID,RELATE_TYPE having count(*) > 1) and rowid not in (select min(rowid) from ops_service_relate group by SERVICE_ID,RELATE_ID,RELATE_TYPE having count(*)>1);