On Mon, Sep 12, 2011 at 6:48 PM, Phoenix Kiula <phoenix.kiula@xxxxxxxxx> wrote: > I have a column in my table: > user_id varchar(100) ; > > This can be NULL, or it can have a value. If it has a value during > INSERT or UPDATE, I want to check that the user exists against my > "Users" table. Otherwise, NULL is ok. (Because the functionality in > question is open to both unregistered and registered users). > > Any idea on how I can implement a FOREIGN KEY constraint? This sounds like an ordinary foreign key constraint. Just be sure that you drop the null constraint on the table's user_id column. So: ALTER TABLE "my table" ADD CONSTRAINT "my table_Users_user_id_fkey" FOREIGN KEY (user_id) REFERENCES "Users" (user_id) ON UPDATE CASCADE ON DELETE SET NULL, ALTER COLUMN user_id DROP NOT NULL; -- Regards, Richard Broersma Jr. -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
