Oracle row_number() over()解析函数高效实现分页

代码如下:
create table T_NEWS
(
ID NUMBER,
N_TYPE VARCHAR2(20),
N_TITLE VARCHAR2(30),
N_COUNT NUMBER
)
prompt Disabling triggers for T_NEWS...
alter table T_NEWS disable all triggers;
prompt Loading T_NEWS...
insert into T_NEWS (ID, N_TYPE, N_TITLE, N_COUNT)
values (1, 'IT', '爱it1', 100);
insert into T_NEWS (ID, N_TYPE, N_TITLE, N_COUNT)
values (2, '体育', '爱体育1', 10);
insert into T_NEWS (ID, N_TYPE, N_TITLE, N_COUNT)
values (3, '体育', '爱体育2', 30);
insert into T_NEWS (ID, N_TYPE, N_TITLE, N_COUNT)
values (4, 'IT', '爱it2', 300);
insert into T_NEWS (ID, N_TYPE, N_TITLE, N_COUNT)
values (5, 'IT', '爱it3', 200);
insert into T_NEWS (ID, N_TYPE, N_TITLE, N_COUNT)
values (6, '体育', '爱体育3', 20);
insert into T_NEWS (ID, N_TYPE, N_TITLE, N_COUNT)
values (7, '体育', '爱体育4', 60);
commit;

第一步：我先用rownum
--分页 row_number，不是rownum
--根据n_count从大到小排列，每页3条
SELECT ROWNUM r,t.* FROM t_news t
WHERE ROWNUM<=3
ORDER BY t.n_count DESC
--问题：为什么order by以后，行号是乱的？
SELECT ROWNUM r,t.* FROM t_news t
--原因：先分配了行号，再根据n_count排序
--所以必须排序，再生成行号
SELECT ROWNUM r,t.* FROM (
SELECT t.* FROM t_news t ORDER BY t.n_count DESC ) t
--分页
--err
SELECT ROWNUM r,t.* FROM (
SELECT t.* FROM t_news t ORDER BY t.n_count DESC ) t
WHERE r between 1 AND 3
--第1页
SELECT ROWNUM r,t.* FROM (
SELECT t.* FROM t_news t ORDER BY t.n_count DESC ) t
WHERE ROWNUM between 1 AND 3
--第2页
SELECT ROWNUM r,t.* FROM (
SELECT t.* FROM t_news t ORDER BY t.n_count DESC ) t
WHERE ROWNUM between 4 AND 6
--error: ROWNUM必须从1开始！
SELECT k.* FROM (
SELECT ROWNUM r,t.* FROM (
SELECT t.* FROM t_news t ORDER BY t.n_count DESC ) t
) k
WHERE r BETWEEN 4 AND 6
--麻烦，效率低！

*****第二步:我用row_number() over()函数
select t2.* from
(select t.*,row_number()over(order by t.n_count desc) orderNumber from t_news t order by t.n_count desc)t2 where orderNumber between 1and 3;

*****************************************************************************************************************************************88
SELECT * FROM (
SELECT t.*,row_number() over(ORDER BY n_count DESC) r
FROM t_news t
ORDER BY t.n_count DESC
) t
WHERE r BETWEEN 4 AND 6
--通用语法： 解析函数() over(partition by 字段 order by 字段) 您可能感兴趣的文章:oracle,mysql,SqlServer三种数据库的分页查询的实例Oracle实现分页查询的SQL语法汇总Oracle中使用Rownum分页详细例子oracle 分页 很棒的sql语句浅析Oracle和Mysql分页的区别Oracle与Mysql主键、索引及分页的区别小结Oracle、MySQL和SqlServe三种数据库分页查询语句的区别介绍分页技术原理与实现之Java+Oracle代码实现分页(二)oracle分页存储过程 oracle存储过程实例oracle实现一对多数据分页查询筛选示例代码

over number 函数 Oracle 解析函数 分页