> If we call it a state or a value doesn't really matter if you just keep
> in mind that NULL means "unknown". I mean, to most of us "the state of
> unknown" is pretty much the same thing as "an unknown value". I know
> there's a technical difference, but the point of this thread is to gain
> an intuitive understanding of how NULL affects expression evaluations in
> SQL, and at least to me "state" doesn't help. Thinking "unknown" does.
>
> Kjell

yes - thinking "unknown" helps you understand that you can't test for
equality of 2 unknown values.
But if the "state" of 2 things is NULL, then I argue they should be equal in
the same way that the last character on the end of all my C strings are the
same! I can see that last character if I do a low level read on the disk -
it's there and it's always the same bit sequence. :-)
Alan