On 2013-04-11, Matthias Nagel <matthias.h.na...@gmail.com> wrote: > Hello, > > is there any best practice method how to create a foreign key that only > allows values from those rows in the referenced table that fulfill an > additional condition?
tes. make the key wide enough to capture this state. I dom't like it either. or partition the child table (which may not work for other constraints) > First I present two pseudo solutions to clarify what I would like to > do. They are no real solutions, because they are neither SQL standard > nor postgresql compliant. The third solution actually works, but I do > not like it for reason I will explain later: > FOREIGN KEY ( parent_id, 42 ) REFERENCES parent ( id, discriminator ) I have wanted this before too. > FOREIGN KEY ( parent_id ) REFERENCES ( SELECT * FROM parent WHERE discri I hadn't thought of expressing it like that. or similarly using a view instead of a select. but I think I have tried FOREIGN KEY ( parent_id ) REFERENCES parent ( id ) where discriminator = 42 and it didn't work. -- ⚂⚃ 100% natural -- Sent via pgsql-sql mailing list (pgsql-sql@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-sql
