Jeff Davis wrote:
> On Mon, 2012-06-04 at 11:56 -0400, Bruce Momjian wrote:
>
>> I get your point about COUNT(*) really counting rows, not values, but
>> why doesn't GROUP BY then skip nulls?
>>
>
> A while ago, I came to the conclusion that applying logic to extrapolate
> the behavior of NULL is a bad idea:
>
> http://thoughts.davisjeff.com/2009/08/02/what-is-the-deal-with-nulls/
>
> Jose was not wrong about the inconsistency between UNIQUE and GROUP BY.
> But the answer is that "we do it that way because the standard says so".
> And that's a good reason.
>
> Regards,
> Jeff Davis
>
>
>
The article pointed by Jeff is very insightful.
NULLs, if you know them, avoid them :-(
I agree with Date and Darwen about NULLs:
"Chris Date and Hugh Darwen the authors of The Third Manifesto, have
suggested that the SQL Null implementation is inherently flawed and
should be ELIMINATED altogether^
<http://en.wikipedia.org/wiki/Null_%28SQL%29#cite_note-3rdmanifesto-16>
, pointing to inconsistencies and flaws in the implementation of SQL
Null-handling (particularly in aggregate functions) as proof that the
entire concept of Null is flawed and should be removed from the
relational model"
j