@Dušan Pavlica; I must say thank you. This is really interesting, and in the 7 years I've been using mysql and sql, I've never know this (or had, but didn't realize what I had done). This little bit of information could make for some interesting changes to a couple of my projects I am working on, where I've done this, but done it in code, rather than in mysql.
Steven Staples > -----Original Message----- > From: Dušan Pavlica [mailto:pavl...@unidataz.cz] > Sent: June 29, 2010 11:26 AM > To: Victor Subervi > Cc: mysql@lists.mysql.com > Subject: Re: Two Primary Keys > > Hi, > > try this and you will see exactly how autoincrement behaves in MyISAM > tables when it is part of primary key. > > 1) declare table like this: > CREATE TABLE `test_tbl` ( > `field1` int(10) unsigned NOT NULL default '0', > `field2` int(10) unsigned NOT NULL auto_increment, > `field3` char(10) NOT NULL default '', > PRIMARY KEY (`field1`,`field2`) > ) ENGINE=MyISAM; > > 2) then insert some values > INSERT INTO test_tbl (field1, field3) > VALUES(1,'test1'),(2,'test2'),(1,'test3'),(2,'test4'); > > 3) see what's in the table > SELECT * FROM test_tbl ORDER BY field1; > > result is: > 1, 1, 'test1' > 1, 2, 'test3' > 2, 1, 'test2' > 2, 2, 'test4' > > field2 is unique only in context of field1. > > Hth, > Dusan > > > > Victor Subervi napsal(a): > > 2010/6/29 João Cândido de Souza Neto <j...@consultorweb.cnt.br> > > > > > >> As far as I know, if you have an auto_increment primary key, you cant > have > >> any other field in its primary key. > >> > >> > > > > Makes sense. Actually, I was just copying what someone else gave me and > > adding the auto_increment, then I got to wondering, what is the purpose > of > > having two primary keys? > > TIA, > > V > > > > > > -- > MySQL General Mailing List > For list archives: http://lists.mysql.com/mysql > To unsubscribe: http://lists.mysql.com/mysql?unsub=sstap...@mnsi.net > > No virus found in this incoming message. > Checked by AVG - www.avg.com > Version: 9.0.830 / Virus Database: 271.1.1/2917 - Release Date: 06/29/10 > 02:35:00 -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/mysql?unsub=arch...@jab.org
