Selecting TOP N - Performance Issue

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Selecting TOP N - Performance Issue

Author

Topic

keyursoni85
Posting Yak Master

233 Posts

Posted - 2013-09-07 : 05:08:52

Hi,

I am selecting TOP 1 record (last inserted) but I feel that it gives some performance effect. Because that table included millions of rows and TOP 1 downgrades performance.

I have given two ways for selecting TOP last one. Please suggest best way.



SELECT  [COLUMNS]....
FROM   LARGETABLE L 
	 inner join
	     (	select MAX(ID) maxchid
		from LARGETABLE
		where REFID = 1654424) chInner
	 on chInner.maxchid = ch.ID

---------------------------------

SELECT  TOP 1 [COLUMNS]....
FROM   LARGETABLE L 
WHERE  REFID = 1654424
ORDER  BY ID DESC

James K
Master Smack Fu Yak Hacker

3873 Posts

Posted - 2013-09-07 : 08:35:33

Do you have any indexes on the table? An index on REFID, ID would help.

jackv
Master Smack Fu Yak Hacker

2179 Posts

Posted - 2013-09-07 : 11:08:28

Have you checked the execution plans?Are there any clues which you can share

Jack Vamvas
--------------------
http://www.sqlserver-dba.com

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