As I discovered recently, thanks to another user on this list, there is at least one situation where you WILL need to also create a KEY index on a PRIMARY KEY column -
If you have a composite primary key such as (col1, col2) and you wish to place a foreign key on col2, you will ALSO have to add a KEY on col2 to be able to do so. Cheers, Matt. -----Original Message----- From: Eldon Ziegler [mailto:[EMAIL PROTECTED] Sent: 11 April 2004 08:53 To: [EMAIL PROTECTED] Subject: Re: Do I specify a primary key to be primary, unique and index ? From the MySQL documentation: * A PRIMARY KEY is a unique KEY where all key columns must be defined as NOT NULL. KEY is a synonym for INDEX. So, specifying PRIMARY KEY implies UNIQUE and INDEX.. You don't have to specify them yourself. At 01:11 am 4/11/2004, you wrote: >I learned that there are three types of indexes (PRIMARY, UNIQUE, and >INDEX). > >Now assuming I create a performance-critical PRIMARY key, will I better have >to specify UNIQUE and INDEX for this column also !? It should be obvious >that a primary key is unique anyway, and an index as well, shouldnt it !? >Please note, I am not after saving disk space here, performance is all I am >after, and such a three-fold indexing exercise just seems redundant to me in >the best case scenario, or harmful even, am I right there !? > > > >-- >MySQL General Mailing List >For list archives: http://lists.mysql.com/mysql >To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED] -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED]
