創(chuàng)建兩張表先單獨插入兩條數(shù)據(jù)

然后批量插入部門號為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)

測試語句

開始驗證in和exists和join
先比較個占比多的部門，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') ;

跟真實執(zhí)行計劃基本一樣，所以之后的都用autotrace來看
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)建兩個簡單索引來測試下

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為統(tǒng)計信息不全，收集下統(tǒng)計信息

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) ;

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 ;

在簡單比較下時間

可以看出在相同條件下，執(zhí)行計劃是相同的，時間消耗也是一樣的
因為有朋友說not exists的子查詢會走索引not in索引失效，所以not exists會快，所以為了說服他又做了點補充

并沒有什么差別。而且not in和not exists都會使索引失效，但是不影響子查詢的索引使用！！！！所以直接說誰比誰快的都是不負責(zé)任的說法，還是要具體情況具體分析。分情況使用。那些說not exists比not in快的，這種情況很多，因為不同的原因造成他們的sql的執(zhí)行計劃不同了，所以效率也不同了

拋開執(zhí)行計劃和實際情景，不考慮數(shù)據(jù)情況，數(shù)據(jù)量、索引情況甚至統(tǒng)計信息等這些因素，直接說哪一種比較快都是不靠譜的

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