Re: Newbie question about db normalization theory: redundant keys OK?

"Brian Selzer" <brian_at_selzer-software.com> wrote in message news:Au09j.31688$JD.5283_at_newssvr21.news.prodigy.net...
>
> "David Cressey" <cressey73_at_verizon.net> wrote in message
> news:ncR8j.287$qv1.250_at_trndny01...
>>
>> "Bob Badour" <bbadour_at_pei.sympatico.ca> wrote in message
>> news:4763dc87$0$5291$9a566e8b_at_news.aliant.net...
>> [snip]
>>
>>> 6NF:
>>> R1(a*,b)
>>> R2(a*,c)
>>>
>>> 6NF has at most one non-key attribute.
>>
>> Thanks for the above definition. It's simple, and easily understood. I
>> actually "invented" this form on my own in my head, but didn't think it
>> was
>> important enough to merit giving it a name.
>>
>
> It's also wrong. Consider,
>
> R(a*,b*,c*) where a*, b* and c* are each keys,
>
> R is not in 6NF because it can be decomposed into
>
> R1(a*,b*) and
> R2(a*,c*)
>
> even though R doesn't have any non-key attributes!
>

Wrong in what way? Your example doesn't contradict Bob's statement that: "6NF has at most one non-key attribute".

-- 
David Portas