Oracle利用rowid删除表中重复记录

先看表myemp

查出有重复数据的记录

查出没有重复数据的记录

查出不重复的记录

或者

select * from myemp e where rowid = (select max(rowid) from myemp e2 where e.userid = e2.userid and e.username = e2.username and e.salary = e2.salary)