May 22, 2009 at 9:16 am
OK so I was wondering, how is this query being executed? The only reason why I ask is the implicit conversions that are occurring. I understand the datetime one. But I don't understand the Implicit conversion to an Int for Param 1.
Does your query handle that as
where stat_no = 11
Or
where stat_no = '11'
Granted it shouldn't make that much of a difference, but every little bit helps right? When I use an integer column as a predicate, I only see the conversion with the second example because it's being passed as a character string instead of an integer.
-Luke.
May 22, 2009 at 9:21 am
Hi Carl,
I hope I haven't wasted your time here, I've got some test data on my machine and I'm gonna try and play around but I think what you have is ok.
Here is a good article that Gail wrote about Index Seeks and Index Scans and how they can be misleading sometimes, I haven't actually checked to see if this applies to your code yet , but it might be worth you checking it out:
http://sqlinthewild.co.za/index.php/2009/03/05/when-is-a-seek-actually-a-scan/
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Try to learn something about everything and everything about something. - Thomas Henry Huxley
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May 22, 2009 at 9:42 am
OK time for some sleep, I've lost my marbles... Sorry Carl, I'll try have another look at this next week if you still need.
(Bookmark lookups don't happen with Clustered Indexes[hence there isn't one here] - Please tell me I'm right 🙂 )
Have a good week-end
----------------------------------------------
Try to learn something about everything and everything about something. - Thomas Henry Huxley
:w00t:
Posting Best Practices[/url]
Numbers / Tally Tables[/url]
May 22, 2009 at 9:47 am
Christopher Stobbs (5/22/2009)
OK time for some sleep, I've lost my marbles... Sorry Carl, I'll try have another look at this next week if you still need.(Bookmark lookups don't happen with Clustered Indexes[hence there isn't one here] - Please tell me I'm right 🙂 )
Have a good week-end
Correct. The leave nodes of the Clustered Index are the datapages, not need to "go to" them to access the data.
May 22, 2009 at 10:07 am
Thanks Lynn 🙂
(Chris finds some of his marbles)
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Try to learn something about everything and everything about something. - Thomas Henry Huxley
:w00t:
Posting Best Practices[/url]
Numbers / Tally Tables[/url]
May 22, 2009 at 10:09 am
Effectively, since the leafs of the clustered index contains the actual rows of the table, you don't need a bookmark lookup.
Thank's for your help.
Carl
May 30, 2009 at 11:12 am
Just to check with you..
Is the index order is a per column selectivity?..at times it does make a difference....
Regards,
Raj
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