Re: Oracle query optimizer

From: Winnie Liu <poohland_at_hotmail.com>
Date: Tue, 7 Jul 1998 20:40:12 -0700
Message-ID: <6nupf1$cgk@sjx-ixn6.ix.netcom.com>

If you are using rule-based optimizer, yes, you must write your SQL statment carefully by putting the largest tables at a certain position. But if you are running cost-based optimizer, no, you don't have to worry about that kind of issues. Oracle will automatically choose the path which has the lowest cost (that means, access the fewest data blocks). But in order for Oracle to do that, you need to analyze your tables frequently, building histograms for all your tables. And change the parameter OPTIMIZE_MODE be COST (not rule).

Winnie Liu

Roger Tomas wrote in message <359AADF7.40ACDF81_at_agcs.com>...
>Am new to Oracle and am wondering how smart the query
>optimizer is. Will I have to care about table order, column
>order, etc.?
>
>I saw one post that mentioned joining the largest table last.
>Do I really have to worry about these kinds of issues?
>
>Roger Tomas
>AG Communication Systems
>
>
Received on Tue Jul 07 1998 - 22:40:12 CDT