oracle删除重复数据只保留一条

-- 如表role_user的数据

ROLEID       USERID
  15       88010000000074
  15       88010000000074
  15       88010000000074    

-- 删除相同记录只剩下一条记录

根据两个字段查询重复数据 (roleid，userid)

select * from role_user a where (a.roleid,a.userid) in(select roleid,userid from role_user group by roleid,userid having count(*) > 1)

删除重复数据只保留一条

delete from role_user where rowid not in (select min(rowid) from role_user group by roleid , userid )

下面的只根据userid进行查询与删除

select count(1),USERID from role_user group by USERID HAVING count(1)>1 

DELETE from role_user WHERE (userid) IN ( SELECT userid FROM role_user GROUP BY userid HAVING COUNT(userid) > 1) AND ROWID NOT IN (SELECT MIN(ROWID) FROM role_user GROUP BY userid HAVING COUNT(*) > 1);