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Index [message #280996] Thu, 15 November 2007 06:24 Go to next message
webadministrator
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Registered: October 2005
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Hello,
i am creating indexes on queries. i have 2 seperate queries but on the same table as follows: the first query contains: code_a, code_b and the second query contains code_b, code_c

my question is: should i create one index that combines all the fileds in both queries or is it better to create to different indexes?

Thank you.
Re: Index [message #281014 is a reply to message #280996] Thu, 15 November 2007 07:03 Go to previous messageGo to next message
Michel Cadot
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It depends on many things like counts, frequencies, histogram...
And first what does mean "contains"? Does this mean there are conditions on them?

Regards
Michel
Re: Index [message #281017 is a reply to message #281014] Thu, 15 November 2007 07:07 Go to previous messageGo to next message
webadministrator
Messages: 45
Registered: October 2005
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Thank you for your reply.

yes there are conditions. i mean for example
query 1: ... where code_a = 'a' and code_b ='b'
query 2: ... where code_b is null and code_c ='c'

shall i create them all in one index or seperate them?

Thanks
Re: Index [message #281020 is a reply to message #281017] Thu, 15 November 2007 07:20 Go to previous messageGo to next message
Michel Cadot
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Michel Cadot

It depends on many things like counts, frequencies, histogram...

This for the appropriateness of creating indexes and which one.

Do you want an accurate answer or a quick one?
Quickly answer: 2 indexes (code_a, code_b) (or the opposite depending on...) and (code_c, code_b).

Regards
Michel

[Updated on: Thu, 15 November 2007 07:34]

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Re: Index [message #281026 is a reply to message #280996] Thu, 15 November 2007 07:29 Go to previous messageGo to next message
webadministrator
Messages: 45
Registered: October 2005
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Im sorry i am a bit new to all this index thing.
I would apreciate it if you can give me a small explanation for your answer. is it to enhance the prefomance and speed? and does the order of the fields in the same index count?

thank you
Re: Index [message #281030 is a reply to message #281026] Thu, 15 November 2007 07:35 Go to previous message
Michel Cadot
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Location: Nanterre, France, http://...
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How to Identify Performance Problem and Bottleneck

Regards
Michel

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