Re: [PHP-DB] Group by

Hi i recommend always use indexes when programming. developers tend not
to.. and when the databases grows it's difficult to modify or make them
modify the code.



El mié, 09-12-2009 a las 14:22 -0300, Julio Araya escribió:
> 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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> >
> 
> 
> 
> -- 
> Julio Araya C.                                                Linux User #386141
> Memorista de Ingeniería Civil Informática          Ubuntu User #14778
> Universidd Técnica Federico Santa María         Valparaíso - Chile
>