johnnyk Posted June 26, 2006 Share Posted June 26, 2006 What's the difference between UNIQUE and PRIMARY KEY? Link to comment https://forums.phpfreaks.com/topic/12892-mysql-unique/ Share on other sites More sharing options...
Barand Posted June 26, 2006 Share Posted June 26, 2006 A table can have only one PRIMARY KEY and it is always UNIQUE.You can also have several other indexes which may be UNIQUE or not. Link to comment https://forums.phpfreaks.com/topic/12892-mysql-unique/#findComment-49555 Share on other sites More sharing options...
johnnyk Posted June 26, 2006 Author Share Posted June 26, 2006 So if I just need one unique column, should I use primary key?Also, I saw a tutorial online that defined one column as primary key and unique id. It looks like this:[code]create table myBlobs(blobId int auto_increment not null,blobTitle varchar(50),blobData longblob,blobType varchar(50),primary key(blobId),unique id(blobId));[/code][a href=\"http://www.devarticles.com/c/a/MySQL/Blobbing-Data-With-PHP-and-MySQL/1/\" target=\"_blank\"]http://www.devarticles.com/c/a/MySQL/Blobb...HP-and-MySQL/1/[/a]Why would they define it as primary key and unique? Link to comment https://forums.phpfreaks.com/topic/12892-mysql-unique/#findComment-49783 Share on other sites More sharing options...
Barand Posted June 26, 2006 Share Posted June 26, 2006 Because they don't know what they are doing.[!--quoteo--][div class=\'quotetop\']QUOTE[/div][div class=\'quotemain\'][!--quotec--]So if I just need one unique column, should I use primary key?[/quote]Yes Link to comment https://forums.phpfreaks.com/topic/12892-mysql-unique/#findComment-49804 Share on other sites More sharing options...
johnnyk Posted June 26, 2006 Author Share Posted June 26, 2006 [!--quoteo(post=388209:date=Jun 26 2006, 04:44 PM:name=Barand)--][div class=\'quotetop\']QUOTE(Barand @ Jun 26 2006, 04:44 PM) [snapback]388209[/snapback][/div][div class=\'quotemain\'][!--quotec--]Because they don't know what they are doing.[/quote]Hah. Alright, thanks. Link to comment https://forums.phpfreaks.com/topic/12892-mysql-unique/#findComment-49820 Share on other sites More sharing options...
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