１.rownum 分页：

(select * from emp)

２.显示rownum [oracle 分配的]

select a1.*,rownum rn from (select * from emp ) a1

3. 显示rownum 》６　《＝１０

select a1.*,rownum rn from (select * from emp ) a1　where rownum<=10;

select *  from (select a1.*,rownum rn from (select * from emp ) a1　where rownum<=10)  where rn>=6;

４.几个查询的变化

a. 指定查询的列，只需要修改最里层的子查询；

select *  from (select a1.*,rownum rn from (select ename,sal  from emp ) a1　where rownum<=10)  where rn>=6;

b.如何排系,只需要修改最里层的子查询　order by ：

select *  from (select a1.*,rownum rn from (select ename,sal  from emp  order by sal ) a1　where rownum<=10)  where rn>=6;

select *  from (select a1.*,rownum rn from (select ename,sal  from emp  order by sal desc ) a1　where rownum<=10)  where rn>=6;