Re: When does a query use an Index?

John Smith wrote:
>
> I have looked through all the books I have and can't find a definitive
> answer.
>
> 1. Does a query use an Index when LIKE is used?
>
> 2. Does a query use an Index when an outer join is performed?
>
> 3. Does an Index get used when a view is used? The book says 'under
> certain conditions an Index will not be used' but doesn't say what they
> are.
>
> Can anyone answer these please?
>
> Thanks,
>
> Andy Horne

That's all right what Dan Clamage <clamage_at_mime.dw.lucent.com> wrote in his reply. The explain plan statement shows you the execution plan for a statement.
You may display the execution plan graphically as an outline view after creating the PLAN_TABLE with our Hora tool. (Free trial at www.keeptool.swn.de)
For analysing more SQL statements you can also use the output of Oracle's TKPROF utility. You have to turn on sql_trace in the init.ora file and then restart the rdbms. Then you can switch the sql_trace on for a session by the ALTER SYSTEM command, using a PL/SQL package or also with Hora.

Regards
Holger Heidenbluth

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