Re: Group by
| From: | Julio Araya | Date: | Wed, 09 Dec 2009 17:22:21 +0000 |
| Subject: | Re: Group by | ||
| References: | 1 | Groups: | php.db |
| Request: | Send a blank email to php-db+get-46665@lists.php.net to get a copy of this message | ||
On Wed, Dec 9, 2009 at 12:52 PM, Philip Thompson <philthathril@gmail.com> 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
> --
> PHP Database Mailing List (http://www.php.net/)
> To unsubscribe, visit: http://www.php.net/unsub.php
>
>
--
Julio Araya C. Linux User #386141
Memorista de Ingeniería Civil Informática Ubuntu User #14778
Universidd Técnica Federico Santa María Valparaíso - Chile