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 >>>queries. >>> >>>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 > database. > > Thanks both, > > Yannick > >
Is it a multi-field index ? some versions of phpmyadmin show that messages also if only one field is duplicated. example: 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` (`anno_dep`,`id_cns`,`generale`,`particolare`), UNIQUE KEY `idx_cns_par_anno` (`id_cns`,`anno_dep`,`tipo`,`particolare`,`bis`) ) 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. Regards, Francesco -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED]
