14일차 # 6-20: Delete Case (Correlated DELETE)

  문제: 데이터가 중복일 경우 하나만 남기고 제거하기

drop table e1 purge;

create table e1 as select * from emp;

insert into e1 select * from emp;

insert into e1 select * from emp;

commit;

select * from e1 order by 1;

select rowid, e1.* from e1 order by empno;

delete from e1 ot

where rowid > (select min(rowid) from e1

              where empno = ot.empno);

select * from e1;