RE: quick FK question
Date: Tue, 15 Dec 2009 14:31:59 -0700
Perfect. Such an easy explanation once it is presented clearly.
From: Stephane Faroult [mailto:sfaroult_at_roughsea.com] Sent: Tuesday, December 15, 2009 2:30 PM To: Sweetser, Joe
Subject: Re: quick FK question
You have answered your own question. The FK says 'any value here must be found in the referenced table'. But as Chris Date would tell you, even if many people speak (wrongly) of "null values", NULL is not a value - it's the absence of a value. Nothing violates no constraints.
Sweetser, Joe wrote:
> I'm having trouble understanding FK's and NULL's. It appears I can
> insert a null value to a foreign key which is not what I would expect.
> Is the "solution" to put NOT NULL on the column definition?