> At 7:48 pm -0500 14/3/06, Rhino wrote:
> >>Ah, so now things become clear, a NULL actually can mean
> >>two things? So much for clarity then...
> >Come on; that's not fair. "Unknown" and "not applicable" are more like
different senses of the same thing, not two opposite things.
> IIRC (but please don't ask for a reference) it has been suggested that
there should be two different types of NULL (value unknown & not applicable)
for just this reason.
Yep. "unknown" and "n/a" are two different things and SQL happens
to "support" them by NULLs. This is confusing at times and more
difficult to handle at least...
The problems with NULLs are numerous. Don't say they aren't, cause
they are. In several SQL functions, NULLs make a difference and
they will bite you every now and then. Especially for "new" people,
which is a clear signal they are confusing.
> I suppose what it boils down to is that although the two main reasons one
might use NULL are *not* the same thing, the outcome (the absence of a
value) *is* the same.
> So you're both right. Sort of.