oracle分頁(yè)查詢語(yǔ)句 oracle為什么做個(gè)分頁(yè)關(guān)鍵字?
oracle為什么做個(gè)分頁(yè)關(guān)鍵字?分頁(yè)的宗旨是控制查詢出來(lái)的數(shù)據(jù)個(gè)數(shù),下面這條語(yǔ)句對(duì)于Oracle分頁(yè)已經(jīng)足夠了。(注:該語(yǔ)句只能用于Oracle)SELECT * FROM (SELECT temp
oracle為什么做個(gè)分頁(yè)關(guān)鍵字?
分頁(yè)的宗旨是控制查詢出來(lái)的數(shù)據(jù)個(gè)數(shù),下面這條語(yǔ)句對(duì)于Oracle分頁(yè)已經(jīng)足夠了。
(注:該語(yǔ)句只能用于Oracle)
SELECT * FROM (SELECT temp.*, ROWNUM RN FROM (SELECT * FROM USERS ORDER BY ID DESC) temp) WHERE RN > 0 AND RN <= 10
SELECT *
FROM (SELECT AA.*, ROWNUM RN
FROM (SELECT * FROM USERS ORDER BY ID DESC) AA)
WHERE RN > 0 AND RN <= 10
oracle數(shù)據(jù)庫(kù)怎么實(shí)現(xiàn)分頁(yè)?
您好:oracle查詢分頁(yè)可分為兩種情況,一種使用的是rownum ,另外一種則是使用 row_number() over(order by column_name desc)。1.使用rownum分頁(yè)查詢,可用以下方式:select t2.* from (select t1.*,rownum as rn from table_name t1 where 1=1 and rownum <= page * page_size) t2 where t2.rn > (page - 1) * page_size2.使用 row_number() over() 分頁(yè)查詢select t2.* from (select t1.*,row_number() over(order by column_name desc) as rn from table_name t1 where 1=1 )t2 where t2.rn > (page-1)* page_size and t2.rn <= page * page_size這種方式,也是可以分頁(yè)的。希望能幫助您!
oracle分頁(yè)查詢,需要排序嗎?
1.如果沒(méi)有分頁(yè),在記錄特別多的時(shí)候,顯示會(huì)很慢;
2.如果數(shù)據(jù)實(shí)在太多,比如幾百萬(wàn)到幾千萬(wàn)甚至上億(我遇到的大部分?jǐn)?shù)據(jù)量大的都在幾百萬(wàn)條),分頁(yè)前通過(guò)select count(*) from table 獲取記錄條數(shù),也不明智; 因?yàn)閹装俪汕f(wàn)條的數(shù)據(jù)統(tǒng)計(jì)一下記錄數(shù)可能也要10秒左右;
3. 記錄特別多,最好不要做排序,一旦排序特比慢: