On Mon, 2001-12-17 at 11:38, Terrence Brannon wrote:
> The Momjian book states:
>
> A single-column foreign key is either NULL or matches a primary key
>
> But the problem I have with this statement is that a primary key
> cannot be null or duplicate. And since the foreign key references
> a value that is neither null or duplicate, how could it ever be
> NULL?
If the foreign key is NULL, it doesn't reference anything. If this is
not a valid condition, the column should be declared as NOT NULL.
--
Oliver Elphick Oliver.Elphick@lfix.co.uk
Isle of Wight http://www.lfix.co.uk/oliver
GPG: 1024D/3E1D0C1C: CA12 09E0 E8D5 8870 5839 932A 614D 4C34 3E1D 0C1C
"For I say, through the grace given unto me, to every man that is among you: Do not think of yourself more
highly than you ought, but rather think of yourself with sober judgement, in accordance with the measure of
faithGod has given you." Romans 12:3
