Re: [GENERAL] Foreign keys

[Stephan Szabo]

On Mon, 27 Aug 2001, Neal Lindsay wrote:

> If I create a columnA in a tableA that "REFERENCES tableB(columnB)" in 
> another table, where column B is not null, does that imply a "NOT NULL" on 
> my columnA?  In other words, does it ensure that the value of A is in the 
> set of values for B, or that the value of A is in the Bs unless A is null?

The latter.  The constraint is satisfied by either a NULL or a value in B.
(Note: For multiple column keys it gets more involved depending on the
match type).



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