Todd It doesn't help the join at all and is in fact redundant but it has the following adavanges
1. Bookmarks/pointers to the link table are consistent with other tables (good for your sanity and ORMs) 2. If the database is extended you only propagate a single column (rather than refactor to do so) Its one of those cases where minimalising the database to 'pure' ER theory may not be the 'best' practice HTH Neven > Hi Neven > > Please clarify. > Are you suggesting that a surrogate key should be added to a link > table??? How does that help a join? > > Surely you mean the surrogate keys from the two tables involved in the > many to many join should be on the link table? > > Todd > >> >> As far as 'link' tables go, (ones that resolve a many to many) again put >> in a surrogate key as well as a composite unique candidate key of the >> foriegn keys, for the same reasons above >> >> HTH >> Neven >> >>> I've seen them alot, worked with them rarely. I was just hoping to >>> open a discussion with people working with experienced DBA's regarding >>> today's standing on the use of composite primary keys. >>> >>> I ask, as I have been given a schema to work with, and will be using a >>> framework for development. CakePHP doesn't support composites at all, >>> and I read alot of troubles in other frameworks to work around them. >>> (to the point of hand rolling queries) >>> >>> Call me lazy, but it just seems to me that in most cases, a singular >>> PK can be found for pretty much any table. But are they are must in >>> certain situations? >>> >>> Regards >>> Aaron Cooper >>> -- >>> NZ PHP Users Group: http://groups.google.com/group/nzphpug >>> To post, send email to [email protected] >>> To unsubscribe, send email to >>> [email protected] >> > > -- > NZ PHP Users Group: http://groups.google.com/group/nzphpug > To post, send email to [email protected] > To unsubscribe, send email to > [email protected] > > > -- NZ PHP Users Group: http://groups.google.com/group/nzphpug To post, send email to [email protected] To unsubscribe, send email to [email protected]
