Re: Partial Index Usage Performance Question

On Oct 6, 8:14 am, digory <dig..._at_gmx.net> wrote:
> Hi
>
> I have a table T with columns A, B, C and an index I over all three
> columns. Further, I have a query which uses columns A and B, but not
> C, i.e.
>
> SELECT * FROM T WHERE a = ? AND b = ?
>
> I gather Oracle is able to use index I even though the last column is
> not used. My question is the following: If I write a query like
>
> SELECT * FROM T WHERE a = ? AND b = ? AND c = ?
>
> with a condition for C that, for the data in T, is known to be true
> always, will that query be generally slower or faster than the one
> above, or is there no difference in performance, or does it depend on
> the complexity of the index?
>
> Thanks for a little insight,
> Peter

Think on this one: http://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:54694913325497

Are you thinking of dynamic SQL? Or trying to come up with simple rules to code in "performance?"

jg

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