> > CREATE TABLE `his_msisdn_imei_activ_hist` ( > > `MSISDN` varchar(23) NOT NULL, > > `ACTIV_IMEI` varchar(20) NOT NULL, > > `ACTIV_PHONE_TYPE` varchar(100) NOT NULL, > > `PREV_IMEI` varchar(20) default NULL, > > `PREV_PHONE_TYPE` varchar(100) default NULL, > > `ACTIV_TIME` datetime NOT NULL, > > PRIMARY KEY (`MSISDN`,`ACTIV_IMEI`,`ACTIV_TIME`) > > ) ENGINE=InnoDB DEFAULT CHARSET=latin1; > > > > This primary key is a bad idea. A VERY VERY bad idea. For starters, a > primary key should have ONE field, not THREE. While it is allowed, it's > not going to help performance at all. Next is that the primary key
Care for a fight over this one? :-) A primary key should be the primary key. If this is 3 columns, or 1 varchar column, it's all fine. I agree with your point of the ACTIV_TIME being a bad candidate for being part of a PK though. Oh, and having multiple columns in a PK does not mean you cannot create additional indices as/if required. All in all, your statement about multiple columns in a PK is a very very bad statement ;-) > should be a numeric field. You've got varchars and datetimes! Yuck! If > you want to enforce a rule such as restricting duplicate values, then > start by creating yourself a sane primary key ( an unsigned int, for > example ), and *THEN* put an index ( with your "don't allow duplicates" > rule ) across your (`MSISDN`,`ACTIV_IMEI`,`ACTIV_TIME`) fields. Martijn Tonies Database Workbench - development tool for MySQL, and more! Upscene Productions http://www.upscene.com My thoughts: http://blog.upscene.com/martijn/ Database development questions? Check the forum! http://www.databasedevelopmentforum.com -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED]
