SQL语句NOT IN优化之换用NOT EXISTS

来源：cnblogs　　作者：呼哈嘿　　时间：2018/10/8 9:03:04　　对本文有异议

NOT IN查询示例（示例背景描述：根据条件查询Questions表得到的数据基本在PostedData表中不存在，为完全保证查询结果在PostedData表中不存在，使用NOT IN）：

SET STATISTICS PROFILE ON; 
SET STATISTICS IO ON; 
SET STATISTICS TIME ON; 
GO
/*--你的SQL脚本开始*/
SELECT  A.Id
FROM    dbo.Questions A WITH ( NOLOCK )
WHERE   A.QuestionState = '正常'
        AND A.CheckTime > '2018-09-29 16:00:00'
        AND A.StateShowID NOT IN ( SELECT   B.IntId
                                   FROM     dbo.PostedData B
                                   WHERE    B.[Type] = 'question' );
/*你的SQL脚本结束*/
GO 
SET STATISTICS PROFILE OFF;
SET STATISTICS IO OFF;
SET STATISTICS TIME OFF;

查询耗时如图：

换用NOT EXISTS 查询示例：

SET STATISTICS PROFILE ON; 
SET STATISTICS IO ON; 
SET STATISTICS TIME ON; 
GO
/*--你的SQL脚本开始*/
SELECT  A.Id
FROM    dbo.Questions A WITH ( NOLOCK )
WHERE   A.QuestionState = '正常'
        AND A.CheckTime > '2018-09-29 16:00:00'
        AND NOT EXISTS ( SELECT B.IntId
                         FROM   dbo.PostedData B
                         WHERE  B.[Type] = 'question'
                                AND A.StateShowID = B.IntId );
/*你的SQL脚本结束*/
GO 
SET STATISTICS PROFILE OFF;
SET STATISTICS IO OFF;
SET STATISTICS TIME OFF;