Re: Much Ado about Nothing

"Bob Badour" <bbadour_at_golden.net> wrote in message <news:DDUl6.818$8e4.195417252_at_radon.golden.net>...

> NULL breaks a large number of mathematical identities that we all take for
> granted. My favourite is:
>
> SUM(A) + SUM(B) = SUM(A + B)
>
> In North America, we spend countless millions of dollars every year drilling
> this fact into the heads of our children. We all spent many hours (from
> first grade on) sorting and counting and grouping and drilling to fully
> internalize the above number fact.

This would mean that SUM(A) should really be Null if any A is Null?

> I have seen far too many self-proclaimed database experts who will argue to
> the death that databases need NULL and duplicate rows for "practical"
> reasons while dismissing the relational model as "just theory". In every
> such case, the person was incapable of recognizing the many and obvious
> negative consequences of NULL and duplicate rows.

Didn't either Codd, Date, or both, demand multiple kinds of Null, such as one for "value exists but is unknown at this time", another for "not applicable", etc.?

As for duplicate tuples in a table being evil, I'm nodding my head to the point of spinal injury, but would this imply that duplicate tuples in all relations are evil, and aren't the result sets from SELECT also considered to be relations? ISTR this from relational algebra.

--
Joe Foster <mailto:jfoster_at_ricochet.net>  Space Cooties! <http://www.xenu.net/>
WARNING: I cannot be held responsible for the above        They're   coming  to
because  my cats have  apparently  learned to type.        take me away, ha ha!