I have two tables t1, and t2 where t2.fid is a foreign key reference to
t1.id. Except in this case only a subset of the values in t1 are valid,
the values in t1 that are valid can be found by doing a:
SELECT t1.id JOIN t3 ON t3.id = t1.id
Is there some way to add this in as a check constraint? I could just
write a pl/pgsql function to perform a check before inserting, but I am
beginning to suspect that the reason I am running into this is because
my schema isn't accurately representing the business logic of the
application.