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Posted by Erland Sommarskog on 09/17/05 21:01
laurenq uantrell (laurenquantrell@hotmail.com) writes:
> I am trying to determine which of three stored procedure designs are
> fastest in the Query Analyzer:
>
> One query is a straight SELECT query with all desired rows and a dozen
> (tblName.RowName = @param or @param = Null) filters in the WHERE
> statement.
@param = Null?
Remember that NULL is never equal to anything, not an even another NULL.
NULL is an unknown value, and two nulls may be two different values.
Use "@param IS NULL" instead.
> Are the Time Statisticts THE HOLY QRAIL as far as determining which is
> fastest, and what so I want to look at, the Vale or the Average? I
> notice there are different numbers of bytse sen and bytes received for
> each of the three queries.
When I need to benchmark queries I usually do:
DECLARE @d datetime, @tookms int
SELECT @d = getdate()
-- Run query
SELECT @tookms = datediff(ms, @d, getdate())
PRINT 'It took ' + ltrim(str(@tookms)) + ' ms.'
As John mentioned it is important to have the cache in mind. You can
do DBCC DROPCLEANBUFFERS to flush the cache, but don't this on a
production box! Often I'm lazy and run the queries several times, and
forget the first run, since that may include time reading from disk.
--
Erland Sommarskog, SQL Server MVP, esquel@sommarskog.se
Books Online for SQL Server SP3 at
http://www.microsoft.com/sql/techinfo/productdoc/2000/books.asp
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