Rod Taylor <rbt@zort.ca> writes:
> On Sun, 2002-09-01 at 04:00, Neil Conway wrote:
> > This patch fixes a minor inaccuracy in the documentation: NOT NULL
> > is not synonymous with CHECK (xxx IS NOT NULL) -- for example,
> > consider ALTER TABLE ADD PRIMARY KEY, which checks for 'NOT NULL',
> > not a check constraint.
>
> Yeah, but they're still synonymous.
How so? Their behavior is clearly different (note the case above, as
well as any other situation in which the system attempts to determine
if a column allows a NULL value).
Since they are not interchangeable, they can't be synonyms.
Cheers,
Neil
--
Neil Conway <neilc@samurai.com> || PGP Key ID: DB3C29FC