So if you have individual indexes for example field_1, field_2 and field_3
etc and then perform a search like
WHERE field_1 = 10
AND field_3 = 'abc'
This wouldn't improve the search ? You have to create a index for all
possible combined field searches ?
On Fri, Oct 1, 2010 at 9:35 PM, Gavin Towey <gto...@ffn.com> wrote:
> You can't use an index to select records in a range, and order them. The
> order by will cause a filesort in that case.
>
> Additionally indexes are always read left to right. So an index on
> ('user_id', 'product_id') will help when doing WHERE user_id=N AND
> product_id IN (1,2,3), but wouldn't help for just the condtion on
> product_id.
>
> See the manual for full details on how mysql uses indexes:
> http://dev.mysql.com/doc/refman/5.1/en/mysql-indexes.html
>
>
> -----Original Message-----
> From: Jonas Galvez [mailto:jonasgal...@gmail.com]
> Sent: Friday, October 01, 2010 11:48 AM
> To: mysql@lists.mysql.com
> Subject: Indexing question
>
> Suppose I wanted to be able to perform queries against three columns of my
> table: 'user_id', 'product_id' and 'created'. Most of the time I'll just be
> range-selecting records from the table ordering by 'created'. But I may
> also
> want to select where 'user_id' = something and 'product_id' in (list, of,
> ids), ordered by 'created'. Do I need two separate indexes, one on
> 'created'
> and another on ('user_id', 'product_id', 'created'), or does having only
> the
> latter suffice the former case?
>
>
> -- Jonas, http://jonasgalvez.com.br
>
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