--- In ib-support@y..., Helen Borrie <helebor@d...> wrote:

> At 11:08 AM 09-04-01 +0200, you wrote:
> >Helen,
> >
> > > >If I define a computed column like the one in documents:
> > > >full_name computed by (first_name || ' ' || last_name)
> > > >It works only if non of the two composing columns is null.

Otherwise, the

> > > >value is null if any of the two is null.
> > >
> > > Correct. Value + NULL evaluates to false.
> >
> >As a matter of fact, Value + NULL evaluates to NULL.
> >I guess you meant that.
>
> No, I meant what I said.

Then I don't understand your reply.

I thought that the original message said "Value + NULL is NULL". You
said "Correct", which I (in my admittedly very simple [and I strive to
keep it that way] mind) took as agreement that "Value + NULL is
NULL/unknown". However, you then continued to say "Value + NULL
evaluates to FALSE".

Either Value + NULL evaluates to NULL/unknown, or Value + NULL
evaluates to FALSE ... even in the SQL standard, you can't have it
both ways.

I can see that you might say that Value + NULL is equivalent to FALSE
in an IF .. THEN ... ELSE ... construct, but even there I'd quibble.
That thinking seems to cause people to get messed up when they write
IF *NOT* ... THEN ... constructs, at least in my experience.

As I said, I don't understand your reply. (And somehow, life will go
on!)

Cheers,
db