Re: How to optimize this query?

On Wed, 06 Aug 2003 10:44:28 GMT, "Edward J. Prochak" <ed.prochak_at_magicinterface.com> wrote:

>My understanding is that the optimizer can decide that if it can answer
>COUNT(*) from table statistics, then it will do so. I hadn't thought about
>using it as a wrapper around the actual query. In that case you are right,
>cause there's no statistics for the optimizer to look at.

 But optimiser statistics (user_tables.num_rows) cannot be used as the basis for COUNT(*), since they are only refreshed periodically; so after the first insert/delete after gathering stats, it would give the wrong answer.

 It's going to have to scan _something_; most likely an index.

--
Andy Hassall (andy@andyh.co.uk) icq(5747695) (http://www.andyh.co.uk)
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