Re: Newbie question about db normalization theory: redundant keys OK?
Date: Sun, 16 Dec 2007 08:44:03 -0000
"Brian Selzer" <brian_at_selzer-software.com> wrote in message
> "David Cressey" <cressey73_at_verizon.net> wrote in message
>> "Bob Badour" <bbadour_at_pei.sympatico.ca> wrote in message
>>> 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
>> 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
> 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 PortasReceived on Sun Dec 16 2007 - 09:44:03 CET