Re: SQL For Smarties 3rd Edition - ATTN Joe Celko

"Jan Hidders" <hidders_at_gmail.com> wrote in message news:1162896540.116752.174410_at_m7g2000cwm.googlegroups.com...
>
> David Cressey wrote:
> >
> > Here's the link to the top level page....
> >
> > http://www.utexas.edu/its/windows/database/datamodeling/rm/overview.html
> >
> > This leads down to E-R modeling, and introduces tables, etc. and also
> > normalization.
>
> Indeed a very nice reference. But ... I'm not very happy with their
> definitions of the normal forms.
>
> http://www.utexas.edu/its/windows/database/datamodeling/rm/overview.html
> wrote:
> > BCNF is based on the concept of determinants. A determinant column is
one on which
> > some of the columns are fully functionally dependent.
> >
> > A relational table is in BCNF if and only if every determinant is a
candidate key.
>
> A determinant is not a column but a set of columns. And then the
> definition should say "for every non-trival FD the determinant is a
> *superkey* " or redefine the concept of "determinant" such that it is
> minimal (like, the left-hand side of an FD such that there is not
> proper subset that is also the left-hand side of an FD).
>
> > A relational table is in the fourth normal form (4NF) if it is in BCNF
and all multivalued
> > dependencies are also functional dependencies.
>
> That should of course say not "all MVDs" but "all *non-trivial* MVDs".
>
> > A table is in the fifth normal form (5NF) if it cannot have a lossless
decomposition into any
> > number of smaller tables.
>
> That is too strict. The requirement is that the decomposition should
> not follow from the CKs.
>
> I wonder if Edsger Dijkstra (who btw. at the end of his career taught
> in Austin at the U. of Texas) would have had something clever and
> inspiring to say about such sloppiness and letting database theory be
> taught as part of a Windows course. :-)
>
> -- Jan Hidders
>

Your points on normalization are well taken. Perhaps the folks who maintain this website can be persuaded to amend it. Perhaps not. Received on Wed Nov 08 2006 - 12:40:58 CET