Re: Trend towards artificial keys (GUIDs) sez my textbook...is AI next?

On Dec 17, 8:02 am, Bob Badour <bbad..._at_pei.sympatico.ca> wrote:

> Ray, there is no simple rule. The design criteria for keys are:
> simplicity, familiarity, stability, uniqueness, irreducibility.
>
> You would do yourself a favour by writing them on a post-it note right
> about now.
>
> Sometimes they conflict and one has to make tradeoffs. The ideal key
> will have all 5 of those properties. Sometimes no such ideal key exists.
> At such times, one must understand why each of the above properties is
> important and what problems will ensue from not having the property.

Bob thanks for that link to the 1989 poster "Five Rules of Normalization" involving the Puppy Kennel. Very useful, I've gone over it several times (still can't figure out Rules 4 or 5 but I'll get it eventually).

Today I learned that Access will not give you an error if you create a relationship (i.e. migrate a primary key to another table as a foreign key) between two tables where the second table has a *compound* primary key that includes a PRIMARY key of the first table (!). I didn't know that you could do that, I assumed you never could use a primary key as the primary key of another table, but it makes sense since you're not really using a primary key again, since the second table has a _compound_ primary key. Now something tells me that this compound key is probably not a good key, since it seems to violate 2NF, but that's another point.

Learn something new everyday.

RL Received on Mon Dec 17 2007 - 20:52:29 CET