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Time Bomb Coding
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Time Bomb Coding
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David.Poole
David.Poole
Posted Tuesday, February 09, 2010 9:27 PM
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Comments posted to this topic are about the item
Time Bomb Coding
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Post #862916
Divya Agrawal
Divya Agrawal
Posted Tuesday, February 09, 2010 11:10 PM
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Excellent Article !! covered almost all points for time bomb coding.
--Divya
Post #862953
ziangij
ziangij
Posted Tuesday, February 09, 2010 11:25 PM
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thanks David
... really good article... i m facing the archiving issue now...
Post #862956
Malcolm Daughtree
Malcolm Daughtree
Posted Tuesday, February 09, 2010 11:40 PM
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If you are really fighting for microseconds
If Exists ( Select Null from bigtable Where ...) also is a good test with minimal Overhead instead of Select 1
Begin
.... fancy code
End
But I still find the best time bombs are what I refer to as 'Surrogate Key' processing where software allows customisations to things like account codes and part numbers and financial processing is carried on a conglomerate of individual elements with no key contraints.
Thanks David, a timely article to point out to my new Developers.
CodeOn
Post #862959
Ryan C. Price
Ryan C. Price
Posted Wednesday, February 10, 2010 12:21 AM
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Not that I want to encourage bad habits, but I seem to recall a discussion (I thought it was here @ SQL Server Central, but I can't find it) regarding COUNT(*) vs EXISTS, and tests were carried out (in SQL 2005 or 2008) where the compiler was smart enough to recognize that a programmer really intended to use EXISTS not COUNT(*), and so actually generated the same execution plan for both - the SQL Server engineering team compensating for the huge amount of abuse of COUNT(*) that goes on.
...But as I said, that's still no excuse for bad programming - the right tool for the job is EXISTS
EDIT:
Forgot to say 'thanks for the cool list of things to look out for' - so, David, thanks for the cool list of things to look out for
Post #862968
SQLRNNR
SQLRNNR
Posted Wednesday, February 10, 2010 12:32 AM
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Nice compilation of some of the practices that make for poorly performing queries.
Jason
AKA CirqueDeSQLeil
I have given a name to my pain...
MCM SQL Server 2008
SQL RNNR
Posting Performance Based Questions - Gail Shaw
Posting Data Etiquette - Jeff Moden
Hidden RBAR - Jeff Moden
VLFs and the Tran Log - Kimberly Tripp
Post #862973
Ritesh Medhe
Ritesh Medhe
Posted Wednesday, February 10, 2010 12:38 AM
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lovely article thx
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dungimon
dungimon
Posted Wednesday, February 10, 2010 1:20 AM
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Brilliant article! opened my eyes to a few practices I hadn't realised were soo poor.
Post #862992
nicholasw
nicholasw
Posted Wednesday, February 10, 2010 1:27 AM
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Instead of:
IF EXISTS(SELECT 1 FROM ......WHERE....)
Would the following be quicker still?
IF EXISTS(SELECT TOP 1 1 FROM ......WHERE....)
Post #862997
Ryan C. Price
Ryan C. Price
Posted Wednesday, February 10, 2010 1:40 AM
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nicholasw (2/10/2010)
Instead of:
IF EXISTS(SELECT 1 FROM ......WHERE....)
Would the following be quicker still?
IF EXISTS(SELECT TOP 1 1 FROM ......WHERE....)
No, and it doesn't really make sense - TOP implies 'importance' i.e. TOP 1 means you're looking for the '1' most 'important' row. When using 'EXISTS', there is no concept of importance - there is data or there isn't.
Also, doesn't TOP get lonely without an 'ORDER BY' clause ?
Post #863001
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