Re: The BOOLEAN data type

"WangKhar" <Wangkhar_at_yahoo.com> wrote in message news:bb269444.0304020146.61cd1019_at_posting.google.com...
> On the true false unknown null question.
>
> There is a definite difference between unknown and null.
>
> Unknown (to me at least) suggests you Dont Know. Null itself suggests
> you dont know whether you know or not.

NULL means different things to different people and different things to the same person in different contexts. In SQL, the semantics sometimes match "unknown" and at other times have truly absurd semantics forcing implicit restriction criteria etc.

Codd tried to plaster over the problems by introducing a second marker for "inapplicable" and further complicating the logic type to use 4VL. Date rightly criticized that at the time for starting the way to an infinite progression of markers.

I see that you and Andrew are "reinventing the wheel" of sorts--or perhaps better "reexploring the back yard".

> as it were...
>
> its a literal null state of knowledge, as opposed to unknown which is
> a positive denial of knowledge.
>
> try posting in a philosophy group for a serious answer on that one....
>
>
> :P is there a database.philosophy group out there?
Received on Wed Apr 02 2003 - 21:03:52 CEST