Re: Where clause order - importance of - rule based optimisation

In my experience with rule base, the order in the from clause is important unless the parse can determine that one index is best. If both tables you are using have the leading column of an index used, it may not be able to determine which is the best index and will go back to the from clause. I feel it is always a good idea to order your from clause in the order in which you want the tables used and if the parse overrides it, your still OK.

Frank Abney                              Email: abneyf_at_osshe.edu

On 8 Apr 1997, Peter McKenzie wrote:

> My experience teaches me that this order is very important ,is bottom up,
> and that the from clause order is meaningless in the presence of a where
> clause which cites at least one indexed column. Many people disagree with
> me and various writers on performance give conflicting advice. Am I
> correct in my assumptions ? Does this rule change from one version of
> Oracle to another. Why is there still so much confusion with regard to
> tuning in the Oracle arena ?
>
>
>
Received on Tue Apr 08 1997 - 00:00:00 CEST