Re: So what's null then if it's not nothing?

vc wrote:
> JOG wrote:
> [...]
> > If you have an integer column, say, that allows nulls, its domain is:
> > {I, Null} (where I represents the integers). While the integers were
> > originally well ordered over the operators that SQL queries, now we
> > have a Null element that is _incomparable_ to anything else in the set,
> > yielding a poset. This to my mind makes a theorem like 3<Null invalid
> > as the two items incomparable. My question is - is this not a stumbling
> > block
>
> Why would it be a stumbling block ? You may (a) not care about null
> ordering; (b) define such order independently of the '<=' predicate.

I don't quite understand this, perhaps you could expand vc. My stumbling block is that Null is simply incomparable with an integer for example - it is like asking whether a sound is less than the colour blue. Yet a select statement may often end up asking this sort of thing in order for it to be resolved - so why would you ever want to create a system, whether it be using 3VL or 2VL with human interpretation, that accomodates such nonsensical questions in the first place? It seems to me that this would be an attempt to alleviate a symptom as opposed to the underlying ill. I am of course open to convincing otherwise.

>
> > before you even reach the point where one can debate whether a
> > 3VL be layered on top? All best, Jim.
Received on Tue Dec 13 2005 - 17:26:44 CET