Re: Which index is used when multiple are valid

Under RBO, the optimizer should choose the rightmost first, so, "B". For best performance, use the index that will return the fewest rows as the rightmost.

"Daniel Roy" <danielroy10junk_at_hotmail.com> wrote in message news:3722db.0311030943.4a1dcd76_at_posting.google.com...
> Hi guys,
> I've been asked a question for which I'm not too sure. We use Oracle
> 9.2, with RBO (we're stuck with that choice because we use Siebel,
> please don't go there...). One of the DBA's asserts that if 2 indices
> are valid for a query, then the one created the latest will be used.
> Here's an example to make things clearer:
>
> select * from my_table where col_a = 'A' and col_b = 'B';
>
> Let's say I have 2 examples on this table: ind_a(col_a, col_b) and
> ind_b(col_b, col_a). Which one will my query use, and why?
>
> Daniel
Received on Mon Nov 03 2003 - 15:05:02 CST