oracle学习笔记三（分页查询）

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本文介绍了Oracle数据库中实现分页查询的多种方法，包括使用ROWNUM进行基础分页、利用ROWID实现特定场景下的分页及通过分析函数ROW_NUMBER()进行高效的数据分段。文章详细解释了每种方法的具体实现步骤，并提供了实际SQL示例。

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