Le lundi 03 octobre 2005 à 16:24 +0200, Bastian Balthazar Bux a écrit :
> 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
> > database.
> > Thanks both,
> > Yannick
> 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.
No, no, it's just a dumb double index :-)
I am pretty sure it is completely useless. Actually I have already