Re: oracle indexes

From: <>
Date: Fri, 06 Jun 2008 03:01:28 GMT
Message-ID: <cM12k.3020$Yx.232@trndny08>

"joel garry" <> wrote in message On Jun 4, 9:01 pm, doug <> wrote:
> Hello,
> Say If I have a table with column a, and column b (say they are
> integers).
> Sometimes I will do a query with a where clause that just references
> column a.
> Sometimes I will do a query with a where clause that references both
> column a and b.
> Is there a need to create an index with a, and an index with a, b? Or
> will an index with a,b work for both of the above types of queries?
> I know in mysql if I have an index (a, b, c), then it is useful for
> queries referencing a or a,b or a, b,c. But, I am not as familiar
> with how Oracle indexes work.
> Thanks.

You should read about indexing in the concepts manual and the performance tuning manual. You can also search for the skip scan Jim mentioned, which answers your question.

Once you become comfortable with the basic concepts, you can delve deeper in many places, especially (be sure and check out the index internals presentation).


-- is bogus.
I just don't understand why kids would do a stupid thing like

I had forgotten to mention Richard Foote's web site.  It is excellent.  Lots 
of fantastic information there.
Received on Thu Jun 05 2008 - 22:01:28 CDT

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