SQL Server 2008：使用内部联接的查询性能

debugcn 发表于 Dev

记忆

在这里，我在查询的海量数据的内部联接上遇到性能问题，如下所示：

例子：

/* Creating table */

create table xyz
(
 colp1 nvarchar(10),
 colp2 nvarchar(10),
 coldt date,
 coltm datetime,
 coldr integer
);

/* Inserting records */ 

insert into xyz values('A','B','2014-08-02','10:00:00',50);
insert into xyz values('A','C','2014-08-02','11:08:08',120);
insert into xyz values('A','B','2014-08-02','11:08:55',160);
insert into xyz values('A','D','2014-08-03','09:00:15',180);
insert into xyz values('A','E','2014-08-04','11:00:10',600);
insert into xyz values('A','F','2014-08-04','11:05:50',320);
.
.
upto 50000

/* Query */

declare @testtable table(dt date,st time,et time)

insert into @testtable select coldt,coltm,DATEADD(ss,coldr,coltm) from xyz

select distinct colp1,colp2,coldt,
            coltm from xyz as x 
            inner join  
            @testtable  as t on convert(varchar,x.coltm,108) > t.st and 
            convert(varchar,x.coltm,108)< t.et;

获得大量时间来执行上述查询以获取海量数据。

zhongxiao37

尝试将查询更改为

create TABLE #testtable (dt date,st time,et time)

insert into #testtable select coldt,coltm,DATEADD(ss,coldr,coltm) from xyz

select distinct colp1,colp2,coldt,
        coltm 
INTO #tmp2
from xyz as x 
inner join  #testtable  as t on convert(varchar,x.coltm,108) > t.st and 
        convert(varchar,x.coltm,108)< t.et;

这里的问题是使用表变量而不是临时表。这是用于比较表变量和临时表的文档。

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