--先排序然后删除第n条数据
delete from scott.emp
where empno in (select empno
from (select *
from scott.emp
where comm is null
and rownum < 2
order by hiredate desc));
--先排序然后更新第n条数据
update scott.emp
set comm = 123
where empno in (select empno
from (select empno
from scott.emp
where rownum < 2
and comm is null
order by hiredate asc));