第一个查询使用EXISTS而第二个查询使用IN。 注 意两个查询返回相同的信息。 USE pubs SELECTDISTINCTpub_nameFROMpublishersWHEREEXISTS(SELECT*FROMtitlesWHEREpub_id=publishers.pub_idANDtype='business') using the IN clause: USE pubs; SELECTdistinctpub_nameFROMpublishersWHEREpub_idIN(SELECTpub_idFROMtitlesWH...
When you write EXISTS in a where clause,you're telling the optimizer that you want the outer query to be run first, using each value tofetch a value from the inner query. In many cases, EXISTS is better because itrequires you to specify a join condition, which can invoke an INDEX scan...
第一个查询使用EXISTS而第二个查询使用IN。注意两个查询返回相同的信息。 USEpubs GO SELECTDISTINCTpub_name FROMpublishers WHEREEXISTS (SELECT* FROMtitles WHEREpub_id=publishers.pub_id ANDtype=/'business/') GO --Or, using the IN clause: USEpubs GO SELECTdistinctpub_name FROMpublishers WHEREpub_id...
第一个查询使用 EXISTS 而第二个查询使用 IN。注意两个查询返回相同的信息。 USE pubs GO SELECT DISTINCT pub_name FROM publishers WHERE EXISTS (SELECT * FROM titles WHERE pub_id = publishers.pub_id AND type = 'business') GO -- Or, using the IN clause: USE pubs GO SELECT distinct pub_name...
USE pubs GO SELECT DISTINCT pub_name FROM publishers WHERE EXISTS (SELECT * FROM titles WHERE pub_id = publishers.pub_id AND type = 'business') GO -- Or, using the IN clause: USE pubs GO SELECT distinct pub_name FROM publishers WHERE pub_id IN (SELECT pub_id FROM titles ...
The execution of SQL query starts from the inner query. Hence in your Query the one in where clause executes first WHERE PNUMBER NOT EXISTS ( SELECT PNO FROM WORKS_ON WHERE ESSN=E.SSN ) based on the result of above query the other query below will run. WHERE NOT EXISTS ( SELECT P...
一、EXISTS 并非总比IN 快，究竟应该选用 IN 还是 EXISTS ，可参考以下分析：1、Select * from t1 where x in ( select y from t2 )相当于 select from t1, ( select distinct y from t2 ) t2 where t1.x = t2.y;2、select * from t1 where exists ( select null from t2 where y ...
2 Conditional Check in Where clause 71 SQL Server: IF EXISTS ; ELSE 95 How to use SQL Select statement with IF EXISTS sub query? 0 putting if exists as a condition in WHERE 0 SQL if statement within WHERE clause 1 SQL Server : IF Condition in WHERE clause 0 SQL Where exists ...
(It also seems like if SQL Server were smarter, it would execute both EXISTS clauses in parallel and let whichever one one completed first short-circuit the other.) Is there a better way to get SQL Server to consistently improve the running time of such a query? Update Thank you for you...
上面的SQL语句IN里面又有NOT EXISTS 这样的情况很难测试同等条件下IN语句和EXISTS语句的效率 还有一个非SARG运算符 在《SQLSERVER企业级平台管理实践》的第424页里提到：SQLSERVER对筛选条件（search argument/SARG）的写法有一定的建议 对于不使用SARG运算符的表达式，索引是没有用的，SQLSERVER对它们很难...