Oracle row_number() over()解析函數(shù)高效實(shí)現(xiàn)分頁

更新時(shí)間：2011年11月15日 23:07:57 作者：

Oracle row_number() over()解析函數(shù)高效實(shí)現(xiàn)分頁，需要的朋友可以參考下。

 
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', '愛it1', 100); 
insert into T_NEWS (ID, N_TYPE, N_TITLE, N_COUNT) 
values (2, '體育', '愛體育1', 10); 
insert into T_NEWS (ID, N_TYPE, N_TITLE, N_COUNT) 
values (3, '體育', '愛體育2', 30); 
insert into T_NEWS (ID, N_TYPE, N_TITLE, N_COUNT) 
values (4, 'IT', '愛it2', 300); 
insert into T_NEWS (ID, N_TYPE, N_TITLE, N_COUNT) 
values (5, 'IT', '愛it3', 200); 
insert into T_NEWS (ID, N_TYPE, N_TITLE, N_COUNT) 
values (6, '體育', '愛體育3', 20); 
insert into T_NEWS (ID, N_TYPE, N_TITLE, N_COUNT) 
values (7, '體育', '愛體育4', 60); 
commit; 

第一步：我先用rownum

--分頁 row_number，不是rownum
--根據(jù)n_count從大到小排列，每頁3條
SELECT ROWNUM r,t.* FROM t_news t
WHERE ROWNUM<=3
ORDER BY t.n_count DESC
--問題：為什么order by以后，行號(hào)是亂的？
SELECT ROWNUM r,t.* FROM t_news t
--原因：先分配了行號(hào)，再根據(jù)n_count排序

--所以必須排序，再生成行號(hào)
SELECT ROWNUM r,t.* FROM (
SELECT t.* FROM t_news t ORDER BY t.n_count DESC ) t

--分頁
--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頁
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頁
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必須從1開始！
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

--麻煩，效率低！

*****第二步:我用row_number() over()函數(shù)
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

--通用語法：解析函數(shù)() over(partition by 字段 order by 字段)

您可能感興趣的文章: