ORACLE分页查询SQL语句(最有效的分页)

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ORACLE分页查询SQL语句(最有效的分页)

2024-06-09 23:52| 来源: 网络整理| 查看: 265

一、效率高的写法

**1.无ORDER BY排序的写法。(效率最高)(经过测试，此方法成本最低，只嵌套一层，速度最快！即使查询的数据量再大，也几乎不受影响，速度依然！)

SELECT * FROM (SELECT ROWNUM AS rowno, t.* FROM emp t WHERE hire_date BETWEEN TO_DATE ('20060501', 'yyyymmdd') AND TO_DATE ('20060731', 'yyyymmdd') AND ROWNUM = 10;

2.有ORDER BY排序的写法。(效率较高)(经过测试，此方法随着查询范围的扩大，速度也会越来越慢哦！)

SELECT * FROM (SELECT tt.*, ROWNUM AS rowno FROM ( SELECT t.* FROM emp t WHERE hire_date BETWEEN TO_DATE ('20060501', 'yyyymmdd') AND TO_DATE ('20060731', 'yyyymmdd') ORDER BY create_time DESC, emp_no) tt WHERE ROWNUM = 10;

二、效率垃圾但又似乎很常用的分页写法

3.无ORDER BY排序的写法。(建议使用方法1代替)(此方法随着查询数据量的扩张，速度会越来越慢哦！)

SELECT * FROM (SELECT ROWNUM AS rowno, t.* FROM k_task t WHERE flight_date BETWEEN TO_DATE ('20060501', 'yyyymmdd') AND TO_DATE ('20060731', 'yyyymmdd')) table_alias WHERE table_alias.rowno = 10; --TABLE_ALIAS.ROWNO between 10 and 100;

4.有ORDER BY排序的写法.(建议使用方法2代替)(此方法随着查询范围的扩大，速度会越来越慢哦！)

SELECT * FROM (SELECT tt.*, ROWNUM AS rowno FROM ( SELECT * FROM k_task t WHERE flight_date BETWEEN TO_DATE ('20060501', 'yyyymmdd') AND TO_DATE ('20060531', 'yyyymmdd') ORDER BY fact_up_time, flight_no) tt) table_alias WHERE table_alias.rowno BETWEEN 10 AND 20;

5.另类语法。(有ORDER BY写法）(语法风格与传统的SQL语法不同，不方便阅读与理解，为规范与统一标准，不推荐使用。)

WITH partdata AS ( SELECT ROWNUM AS rowno, tt.* FROM ( SELECT * FROM k_task t WHERE flight_date BETWEEN TO_DATE ('20060501', 'yyyymmdd') AND TO_DATE ('20060531', 'yyyymmdd') ORDER BY fact_up_time, flight_no) tt WHERE ROWNUM = 10; --6另类语法。(无ORDER BY写法） WITH partdata AS ( SELECT ROWNUM AS rowno, t.* FROM k_task t WHERE flight_date BETWEEN TO_DATE ('20060501', 'yyyymmdd') AND TO_DATE ('20060531', 'yyyymmdd') AND ROWNUM = 10;

三、分析

**Oracle的分页查询语句基本上可以按照本文给出的格式来进行套用。

分页查询格式：

SELECT * FROM (SELECT a.*, ROWNUM rn FROM (SELECT * FROM table_name) a WHERE ROWNUM = 21

其中最内层的查询SELECT * FROM TABLE_NAME表示不进行翻页的原始查询语句。ROWNUM = 21控制分页查询的每页的范围。

上面给出的这个分页查询语句，在大多数情况拥有较高的效率。分页的目的就是控制输出结果集大小，将结果尽快的返回。在上面的分页查询语句中，这种考虑主要体现在WHERE ROWNUM

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ORACLE分页查询SQL语句(最有效的分页)

ORACLE分页查询SQL语句(最有效的分页)

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