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

"Brian Selzer" <brian_at_selzer-software.com> wrote in message news:j9Ocj.1147$El5.530_at_newssvr22.news.prodigy.net...
>
>>> Here is the problem with treating assignment as the only primitive
>>> operation. With assignment, all you have available is the before and
>>> after images of the data, but there may be many different
>>> transformations that could have produced the after image from the before
>>> image, and there's no way to tell which transformation actually
>>> occurred.
>>
>>
>> Yes there is.
>
> I suspect you would have a difficult time proving that.
>

I think I would have no difficulty at all. If you can show a single example where any such information is preserved after an update then I can show you the equivalent assignment to preserve the same information. It ought to be self-evident that such an assignment always exists.

-- 
David Portas