Re: Composite Index Order VS Query Order ?? , Tuning Docs URL ?.

From: Dan Tow <dantow_at_singingsql.com>
Date: Tue, 13 Jul 2004 10:58:00 -0500
Message-ID: <1089734280.40f406881d4d5@www.singingsql.com>

Regarding question #1, if I understand it, you are asking if the order of the WHERE clause conditions needs to match the order of the indexed columns. It does not. WHERE-clause order is irrelevant in all but the most obscure cases. Certainly it is irrelevant in this case. The best reason to worry about WHERE-clause order is just that the order should be easy to read and understand for the human developers maintaining the application - Oracle's optimizers can (and do) perfectly well rearrange the order it checks those conditions to enable the best execution plan and indexes it finds.

Dan Tow
650-858-1557
www.singingsql.com

Quoting "Ranjeesh K R." <ranjeeshk_at_infics.com>:

> Hi,
> I was working on optimising a piece of code which was taking 10hrs + to
> execute and all.So my queries are..
>
> #1) Saw a table where the "order of query" on the table and the "order of
> key"
> are different . For faster results shouldn't they be in the same order.
>
> for eg:
>
> Select ... where A.ID = ... and A.Name = ...
>
> The Key order on this table A NOW is Name & ID Order .
> Shouldn't they be in the order ID , Name ?..
>
>

...

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Received on Tue Jul 13 2004 - 10:55:39 CDT