Re: Not using indexes
From: Mladen Gogala <mgogala_at_yahoo.com>
Date: 14 May 2008 20:38:01 GMT
Message-ID: <482b4da9$0$30640$834e42db@reader.greatnowhere.com>
Date: 14 May 2008 20:38:01 GMT
Message-ID: <482b4da9$0$30640$834e42db@reader.greatnowhere.com>
On Wed, 14 May 2008 21:40:30 +0200, astalavista wrote:
> Why the query below
> doesn't use the indexes ?
> 1 index on FORMID, FORMINDEX, SUBJECTID, VISITID on the each tables.
> Thanks for your lights.
Indexes are not used because you don't have any limiting conditions. You have to read all rows from all the tables. Optimizer has concluded, probably correctly, that it will get the task done faster if it uses the full table scan.
-- http://mgogala.freehostia.comReceived on Wed May 14 2008 - 15:38:01 CDT