Re: Outer joins, performance penalty?

Preston Crawford <prestonc_at_REMOVESPAMBLOCKcrawfordsolutions.com> wrote in message news:<slrnaebb1s.5hr.prestonc_at_serpentor.local>...
> MS SQL Refugee here, so bear with me. I'm new to Oracle and writing a
> function to return a cursor with the result set of a join of multiple
> tables. In MS SQL I'd just use the outer join syntax and I guess I'd never
> thought of the possible penalty of this. In the course of searching online
> for the Oracle syntax, a few people made a reference to the idea that for
> every outer join a table scan is performed on the table being joined in
> optionally. So I'm wondering, is this true? And if it is true, what is the
> solution?

Not true. There are lots of different execution plans for statements with outer joins. Usually index is used when it exists on join columns in outer joined table.

There is no common solution, there is a common approach: wright down your statement, test it for speed. If it is too slow, tune it, starting with printing execution plan.

>
> Preston
Received on Mon May 20 2002 - 12:55:14 CDT