第一步：我先用rownum

--分頁(yè) row_number，不是rownum
--根據(jù)n_count從大到小排列，每頁(yè)3條
SELECT ROWNUM r,t.* FROM t_news t
WHERE ROWNUM<=3
ORDER BY t.n_count DESC
--問(wèn)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(yè)
--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(yè)
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(yè)
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(kāi)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(yǔ)法： 解析函數(shù)() over(partition by 字段 order by 字段)

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