Re: Which normal form is this violating?

"Roger Redford" <dba_222_at_yahoo.com> wrote in message <news:a8c29269.0204242031.9d9964f_at_posting.google.com>...

> Hello DB Design experts,
>
> I'm having the usual disputes about database design issues.
>
> 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)

This might make some sense if Table_A and Table_B correspond to Class_A and Class_B in the application language, with Class_B derived or inheriting from Class_A.

> (Actually, thye have "designed" a number of strange tables,
> and then put views on top of them, to come back to the same one to
> one relationship. Very strange and complex. )

Perhaps someone just really, really dislikes 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.

The normalization rules cover only things that can be formalized enough to eventually automate, while what you're talking about still seems firmly entrenched in "judgement-call" land. <shrug/>

--
Joe Foster <mailto:jlfoster%40znet.com>     Got Thetans? <http://www.xenu.net/>
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