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simple queries VS complex query?

Author

Topic

debradeng
Starting Member

46 Posts

Posted - 2006-12-12 : 16:58:04

I need retrieve data from certain tables.There are two options:1 use one complex query with many table joined together to get all information;or 2 use several simple queries get data from different tables.

From performance and cost view,which way is better and why?

Michael Valentine Jones
Yak DBA Kernel (pronounced Colonel)

7020 Posts

Posted - 2006-12-12 : 17:02:05

The one that runs the fastest is better.

CODO ERGO SUM

debradeng
Starting Member

46 Posts

Posted - 2006-12-12 : 17:12:29

Dear Michael,the reason that I can not decide which is better is because I don't know how to find out which runs faster.Do you have any suggestion?

Thank you!

SwePeso
Patron Saint of Lost Yaks

30421 Posts

Posted - 2006-12-12 : 17:15:48

Timing them?

Peter Larsson
Helsingborg, Sweden

debradeng
Starting Member

46 Posts

Posted - 2006-12-12 : 17:21:12

to Peso,I am using MS SQL 2005.Is there any tools that I can use or you mean "Timing them" manually?

Thank you!

SwePeso
Patron Saint of Lost Yaks

30421 Posts

Posted - 2006-12-12 : 17:25:44

A simple timing device can be this.

Put this BEFORE your code

declare @dt datetime

DBCC DROPCLEANBUFFERS
DBCC FREEPROCCACHE

select @dt = getdate()

<do your thing here>

And put this after your code

select datediff(ms, @dt, getdate()) as Milliseconds

Peter Larsson
Helsingborg, Sweden

debradeng
Starting Member

46 Posts

Posted - 2006-12-12 : 17:52:22

To Peso,
I tried the above method,but ...
"User 'MyDB'does not have permission to run DBCC DROPCLEANBUFFERS.User 'MyDB' does not have permission to run DBCC freeproccache."

I still got the Milliseconds value,I am not sure if it accounts.About the timing device,I have no idea before.Would you like give me some advice,eg. from where I can find more this kind skills etc.

Thank you very much!

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