Yannick Warnier wrote:
> Le lundi 03 octobre 2005 à 12:29 +0200, Martijn Tonies a écrit :
>>>Using PhpMyAdmin, I seldom get the warning message:
>>>PRIMARY and INDEX keys should not both be set for column `ID`
>>>I understand its meaning, but I was wondering to what extent having a
>>>field indexed AND being a primary key might slow down/speed up my
>>>Is that gonna take twice the time if I am searching on the ID field,
>>>just because there are two indexes?
>>>I'd like to have a rough idea of how serioulsy I need to avoid these.
>>Creating a PRIMARY KEY will automatically create an index.
>>Why would you create a second index for that field?
> I'm asking myself the same question. I am working on someone else's
> Thanks both,
Is it a multi-field index ? some versions of phpmyadmin show that
messages also if only one field is duplicated.
CREATE TABLE `tab_sint` (
`id_cns` tinyint(3) unsigned NOT NULL default '0',
`anno_dep` smallint(4) unsigned zerofill NOT NULL default '0000',
`data_dep` smallint(4) unsigned zerofill NOT NULL default '0000',
`particolare` mediumint(8) unsigned NOT NULL default '0',
`generale` mediumint(8) unsigned NOT NULL default '0',
UNIQUE KEY `idx_cns_gen_anno`
UNIQUE KEY `idx_cns_par_anno`
) ENGINE=MyISAM DEFAULT CHARSET=utf8 PACK_KEYS=1 AUTO_INCREMENT=87189031 ;
This schema issue the warning on 'id_cns' but really make sense having 2
indices here since they serves different kind of querys and constraints.