oracle学习笔记三（分页查询）

2cyal9lu40

Oracle分页查询:一共三种方式
1.rownum分页
(select * from emp)
2.显示rownum[oracle分配的]
select a1.*,rownum rn from (select * from emp )a1;


查询1到10行记录
select a1.*,rownum rn from (select * from emp )a1 where rownum<=10;  OR
select * from (select a1.*,rownum rn from (select * from emp )a1 where rownum<=10) ；
查询6到10行记录
select * from (select aa.*,rownum rm from(select * from emp order by sal)aa where rownum<=10) where rm>5;
查询1到5行记录
select * from (select a1.*,rownum rn from (select * from emp )a1 where rownum<=10) where rownum<=5；



4.几个查询变化
A。指定查询列，只需修改最里层的子查询；
B。排序，也只需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;

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


显示4到9的记录
select * from (select a1.*,rownum rn from (select * from emp )a1 where rownum<=9) where rn>=4;


1 要把ROWID来分
select * from t_xiaoxi where rowid in(select rid from select rownum rn,rid from (select rowid rid,cid from t_xiaoxi order by cid desc) where rownum<10000) where rn>9980) order by cid desc;

2 按分析函数来分
select * from (select t.*,row_number() over(order by cid desc) rk from t_xiaoxi t )where rk<100000 and rk>9980;

3 按rownum来分。
select * from (select t.* rownum rn from (select * from t_xiaoxi order by cid desc)t where rownum<10000) where rn>9980;

效率1》3》2


SELECT x.* from (   
     SELECT z.*,rownum numbers from(   
          select * from emp order by sal)z   
     where rownum<10) x   
where x.numbers>5