> My question therefore is, is it possible to create a foreign key that is
> conditional, i.e. only enforce the foreign key where the value in that
> table is not null.
My understanding from reading previous threads on this topic is the answer
is no, however you could make your own pseudo-foreign key using triggers to
do the same job, but only when your column is not null.
Not sure of the performance impact of doing this though - someone else may
be able to advise pros and cons in more detail.
Cheers,
~p
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