How to normalize this?

I've been thinking about a scenario for a few days now, and I still am not sure how this should be normalized. Maybe someone here can help?

The first part is easy. I have five attributes (a, b, c, d, e) and the following FDs: 1. {a, b, c} --> d
2. {a, b, c} --> e
Obviously, just a single relation with all five attributes and (a, b, c) as candidate key.

But then I find that the second FD isn't full. It should be replaced with: 2a. {a, b} --> e
2b. {b, c} --> e

The single relation now obviously violates 2NF. But how to replace it? The only option I see is to remove e from the first relation, and add a relation (a, b, e), with candidate key (a, b). But that does not represent FD 2b, and it allows extensions that would violate it. Nothing I could not fix with additional code in the RDBMS, but I don't like using code to prevent FD violations.

Does anyone know a better way to normalize this set of FDs?

Cheers,
Hugo Received on Fri Feb 08 2013 - 21:33:27 CET