Hi Eric I dunno why people make 100 field tables, sounds a little harsh. I'll keep you in mind the next time i wanna make a 100 field table.
Anyways, just to let you know mysql 4 will be supporting foreign key constraints. And yes thoes other db technologies like postGrep already support key constraints, but i thought (and correct me if i'm wrong) that mysql just performs a little better (maybe because of having no key constraints). But regardless of mysql not supporting foreign keys, i still put them in the defenitions of my tables because i believe it's good for documentation and also if we upgrade to mysql 4 things will be less painful when updating tables to use foreign keys. >Is it such a big deal to use more than one field for a primary key? Two >field keys are only a little slower than single field Primary keys for >selects. Often in linking tables you want to have duplicates of the two >foreign keys right? Not quite sure what you mean by having duplicates of a foreign key. I'm guessing you mean something like this in a linking table: Linking table ______________ authorID, bookID Author table _____________ authorID, firsname, lastname, ... Book table ___________ bookID, name, pubDate, .... Thus the linking table will have a primary key of authorID and the bookID to uniquely id the row in the linking table. However, you can have this: LInking table _____________ 6, 1 7, 1 Author table _____________ 6, Puff, Daddy, ... 7, keanu, reves, ... Book table ___________ 1, Bad acting and rapping cross over, 2000, .... Thus, the book "Bad acting and rapping cross over" is written by Both Puff and Keanu. Therefore you have multiple entries of the book with id 1 in the table. It appears 2 times on 2 different rows, but 2 times within the same column. (My apologies to keanu and puffy fans out there). Good luck with the 100 field tables, and thanks for your reply and all the other replies out there for this message. I'm glad to know that i'm not the only one that thinks having no primary key is NOT a good idea. I'll be sure to give my collegue a mouthful if he bitches about primary keys again. Thanks Desmond _________________________________________________________________ Chat with friends online, try MSN Messenger: http://messenger.msn.com --------------------------------------------------------------------- Before posting, please check: http://www.mysql.com/manual.php (the manual) http://lists.mysql.com/ (the list archive) To request this thread, e-mail <[EMAIL PROTECTED]> To unsubscribe, e-mail <[EMAIL PROTECTED]> Trouble unsubscribing? Try: http://lists.mysql.com/php/unsubscribe.php
