"Roger Redford" <dba_222_at_yahoo.com> wrote in message
news:a8c29269.0204242031.9d9964f_at_posting.google.com...
>
> [...] The information that my coworkers have is say, x and y.
> It has a one to one relationship. Therefore, it
> goes into one and the same table.
>
> Table_A
> Fieldx (pk)
> Fieldy
>
> However, they are arguing that it goes into another table.
>
> Table_A
> Fieldx (pk)
>
> Table_B
> Fieldx (pk)
> Fieldy (not null)
>
> [...] What normal form does this violate? It isn't 1st,
> 2nd, or 3rd. Boyce-Codd maybe? The crazy thing about
> the design texts, is that they rarely cover mistakes
> in design. This is a common one.
Strictly speaking normalization theory is silent here because it usually
assumes that there are no null values. But if we keep in our mind that the
purpose of normalization was to avoid anomalies and redundancy you can see
that there are none here, so no further normalization is required by the
theory. However, there are a few reasons why you might want to avoid null
values and I believe Date gives a few in chapter 18 of his "Introduction
..".
Received on Thu Apr 25 2002 - 09:29:33 CDT
