Re: OCP - Performance Tuning

"Jonathan Lewis" <jonathan_at_jlcomp.demon.co.uk> wrote in message news:b15h9a$lqq$1$8300dec7_at_news.demon.co.uk...
>
>
> I've just been sent the following question from an OCP test,
> and I can't decide whether this is a subtle trap, or a naive
> interpretation of the manuals on the part of the examiner.

But the OCP exams are all about reading the courseware/manuals. Truth doesn't come into it!

>
> I haven't been told whether this is a 'single answer only'
> question, or 'perm any N'. But I assume from the grammar
> that precisely one answer is supposed to be correct.
>
> If you were taking the exam, which one would you put ?
>
> (NB - I didn't say "which one is correct?").
>
> 4. The cost-based optimizer can choose between a nested
> loops join and a sort merge join operation. All tables are
> analyzed and the OPTIMIZER_MODE is set to FIRST_ROWS.
> Which execution plan will be the result?
>
> a. The sort-merge join.
> b. The nested loops join.
> c. This depends on some sort parameter values.
> d. This depends on the number of rows in each table.

I'm going to suggest that the answer is (b), on the grounds that FIRST_ROWS helps encourage the use of indexes, and nested loop joins use indexes to avoid the costs of having to sort-then-merge on-the-fly.

And that's all you need to know from the courseware!

Regards
HJR Received on Tue Jan 28 2003 - 10:49:22 CST