Oracle row_number() over()解析函数高效实现分页建站知
导读:1建站知识Oracle row_number() over()解析函数高效实现分页,需要的朋友可以参考下。如何seo优化推广网站网站建设多少钱。
复制代码 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网站seo优化课程_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 ( 百度seo网站优化SELECT t.* FROM t_n建设网站公司ews 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)相关如何seo优化推广网站网站建设多少钱。声明: 本文由我的SEOUC技术文章主页发布于:2023-05-23 ,文章Oracle row_number() over()解析函数高效实现分页建站知主要讲述高效,分页,Oracle row_number() over网站建设源码以及服务器配置搭建相关技术文章。转载请保留链接: https://www.seouc.com/article/web_5458.html