Re: Why does Oracle need this Index ?

Thanks, your answer helped me very much.

Roger

Thomas Kyte <tkyte_at_us.oracle.com> schrieb in im Newsbeitrag: 37d4b9f8.16722625_at_newshost.us.oracle.com...
> A copy of this was sent to "Roger" <NOrgSPAM_at_mcs-hh.de>
> (if that email address didn't require changing)
> On Mon, 30 Aug 1999 17:25:09 +0200, you wrote:
>
> It sounds like you are using rule based optimizer.
>
> If there is no index on vkplname, then there are no 'good' access paths to
> either of vkprlist or artikel or vkpreise -- they are all equally good.
It must
> full scan ONE of them and then join to the others.
>
> Using RBO -- the order of the tables (in light of the fact that no index
exists
> from which to make a different plan) in the FROM clause is used to drive
the
> order of the tables. It'll use the table on the rightmost of the from
clause --
> vkpreise. As far as the optimizer is concerned that is as good as full
scanning
> either of the other 2 tables (they would have to be full scanned as well).
>
> List the tables in order of preference of scanning -- if you want vkprlist
to be
> scanned -- then put it last in the from clause.
Received on Tue Aug 31 1999 - 14:27:27 CDT