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inner join 和 exists 效率_一个in、exists、join的简单测试

發(fā)布時(shí)間：2023/12/4 编程问答 48 豆豆

生活随笔收集整理的這篇文章主要介紹了 inner join 和 exists 效率_一个in、exists、join的简单测试小編覺(jué)得挺不錯(cuò)的,現(xiàn)在分享給大家,幫大家做個(gè)參考.

創(chuàng)建兩張表先單獨(dú)插入兩條數(shù)據(jù)

然后批量插入部門(mén)號(hào)為10,20,30,40的數(shù)據(jù)各10499099條

然后dept表也插些干擾數(shù)據(jù)

測(cè)試語(yǔ)句

開(kāi)始驗(yàn)證in和exists和join
先比較個(gè)占比多的部門(mén)，再比較占比少的
1、 in 占比多
select count(*) from scott.EMP_TEST e where e.deptno in (select d.deptno from scott.DEPT_TEST d where d.dname='SALES') ;

跟真實(shí)執(zhí)行計(jì)劃基本一樣，所以之后的都用autotrace來(lái)看
2.exists 占比多
select count(*) from scott.EMP_TEST e where exists (select d.deptno from scott.DEPT_TEST d where d.dname='SALES' and e.deptno=d.deptno) ;

3.join 占比多
select count(*) from scott.EMP_TEST e inner join scott.DEPT_TEST d on e.deptno=d.deptno and d.dname='SALES' ;

http://4.in 占比少
select count(*) from scott.EMP_TEST e where e.deptno in (select d.deptno from scott.DEPT_TEST d where d.dname='TEST') ;

5.exists 占比少
select count(*) from scott.EMP_TEST e where exists (select d.deptno from scott.DEPT_TEST d where d.dname='TEST' and e.deptno=d.deptno) ;

6.join 占比少
select count(*) from scott.EMP_TEST e inner join scott.DEPT_TEST d on e.deptno=d.deptno and d.dname='TEST' ;

7.not in 占比多
select count(*) from scott.EMP_TEST e where e.deptno not in (select d.deptno from scott.DEPT_TEST d where d.dname<>'SALES') ;

8.not exists 占比多
select count(*) from scott.EMP_TEST e where not exists (select d.deptno from scott.DEPT_TEST d where d.dname<>'SALES' and e.deptno=d.deptno) ;

9.join 占比多
select count(*) from scott.EMP_TEST e left join scott.DEPT_TEST d on e.deptno=d.deptno and d.dname<>'SALES' where d.deptno is null ;

10.not in 占比少
select count(*) from scott.EMP_TEST e where e.deptno not in (select d.deptno from scott.DEPT_TEST d where d.dname<>'TEST') ;

11. not exists 占比少
select count(*) from scott.EMP_TEST e where not exists (select d.deptno from scott.DEPT_TEST d where d.dname<>'TEST' and e.deptno=d.deptno) ;

12. join 占比少
select count(*) from scott.EMP_TEST e left join scott.DEPT_TEST d on e.deptno=d.deptno and d.dname<>'TEST' where d.deptno is null ;

下面創(chuàng)建兩個(gè)簡(jiǎn)單索引來(lái)測(cè)試下

1、 in 占比多
select count(*) from scott.EMP_TEST e where e.deptno in (select d.deptno from scott.DEPT_TEST d where d.dname='SALES') ;

分析不走索引的原因是因?yàn)榻y(tǒng)計(jì)信息不全，收集下統(tǒng)計(jì)信息

2.exists 占比多
select count(*) from scott.EMP_TEST e where exists (select d.deptno from scott.DEPT_TEST d where d.dname='SALES' and e.deptno=d.deptno) ;