Re: Database Theory - Keys and functional dependencies?

Thank you!

> > Find out all Keys (Primary/Foreign) for the following
Relation-Types
> > and the kind of Normalization (1NF, 2NF, 3NF, BCNF):
> >
> > a) R1 (A,B,C,D)
> > A -> B
> > B -> A
> > AC -> D
>
> I've left the steps of finding the closure sets of attributes and
deriving
> the irreducible sets of dependencies out...
>
> PK - AC
> Alternative candidate key - BC
> 3NF (Not in BCNF because the two candidate keys overlap and have C
attribute
> in common).
>
>
> > b) R2 (A,B,C,D,E)
> > ABC -> D
> > B -> E
> > A -> C
> >
>
> Primary key - AB
> 1NF - Nonkey attributes are not irreducibly dependent on the primary
key.
>
>
> > c) R3 (A,B,C,D,E,F)
> > A -> B
> > D -> B
> > CE -> AD
> > A -> F
>
> Primary key - CE
> 2NF - Meets criteria for 1NF and 2NF, but contains transitive
dependencies.
>
> >
> > Thank you for your support!
>
> Your welcome!
> >
> > Christian Hoecht
> >
>
> HTH,
>
> Dan Guntermann
>
>
Received on Fri Feb 15 2002 - 09:46:19 CET