Re: Can FK be nullable/optional by design?
Date: Fri, 12 Dec 2003 13:06:15 -0500
"Tobes (Breath)" <tobin_dont_spam_me_at_breathemail.net> wrote in message
> "Joe "Nuke Me Xemu" Foster" <joe_at_bftsi0.UUCP> wrote in message
> > Did you really mean to claim that ALL non-nullable attributes MUST
> > 'logically' be included as part of the primary key?!
> Well, not really! I was just throwing in another option - where if the
> existance of one entity is dependent on another, then you can make the PK
> that entity part of a composite key in the dependent entity. It's an
> alternative to just non nullable foreign keys, where the related column(s)
> become part of a primary key, rather than just a foreign key. Sorry, I
> I need to take my anti-waffle pill, can't seem to put a good explanation
> together 8-)
Your bind above demonstrates a very real pitfall of confusing knowledge of a specific tool with knowledge of fundamentals. I have seen numerous people fall into this specific pit throughout my career. I figure at least a 90% chance the tool you know is Erwin, and you are describing their "identifying" vs. "non-identifying" relationships.
Your bind above also demonstrates the dangers of using a graphical crutch in place of real thought and analysis.
I respectfully suggest you will find yourself much more effective if you learn the fundamentals before the tools. Received on Fri Dec 12 2003 - 19:06:15 CET