RE: quick FK question

  • From: "Sweetser, Joe" <JSweetser@xxxxxxxx>
  • To: "Stephane Faroult" <sfaroult@xxxxxxxxxxxx>
  • Date: Tue, 15 Dec 2009 14:31:59 -0700

Perfect.  Such an easy explanation once it is presented clearly.

Much appreciated,
-joe

-----Original Message-----
From: Stephane Faroult [mailto:sfaroult@xxxxxxxxxxxx] 
Sent: Tuesday, December 15, 2009 2:30 PM
To: Sweetser, Joe
Cc: oracle-l@xxxxxxxxxxxxx
Subject: Re: quick FK question

Joe,

   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.

HTH

SF



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?
>
> Thanks,
> -joe
>   





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