Re: [PHP-DB] Group by

On Wed, Dec 9, 2009 at 12:52 PM, Philip Thompson <[email protected]> wrote:
> Hi.
>
> In a mysql query, it is recommended that "GROUP BY" fields be indexed? Using EXPLAIN on one of my queries, I noticed no change between having indexed by GROUP BY field and not indexing it. Any thoughts would be appreciated.
>
> In this example, should `history_field` be indexed...?
>
> SELECT MAX(`timestamp`) AS `max_ts`
> FROM `history`
> WHERE `req_id` = 17 AND `history_record_id` = 35
> GROUP BY `history_field`

always depends on how many records you have, if you have 100-1000
records is very diferent to 100000-500000


>
> Thanks,
> ~Philip
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