On 8/14/07, Alban Hertroys <[EMAIL PROTECTED]> wrote: > *And* you can define compound foreign key constraints, > for example: > > CREATE TABLE employee ( > employee_id serial NOT NULL, > company_id integer NOT NULL, > name text NOT NULL, > CONSTRAINT employee_pk > PRIMARY KEY (employee_id, company_id) > ); > > CREATE TABLE division ( > employee_id integer NOT NULL, > company_id integer NOT NULL, > name text NOT NULL, > CONSTRAINT division_fk > FOREIGN KEY (employee_id, company_id) > REFERENCES employee > ON DELETE SET NULL > ON UPDATE CASCADE > );
You can also have multiple foreign keys to different tables, and to non-primary keys, as long as they are pointing to columns with a unique constraint on them. > Also a nice trick, when performing DDL statements (CREATE TABLE and > friends), you can wrap them in a transaction and commit (or rollback) if > you like the end result (or not). I believe the only exception to that > rule is CREATE DATABASE. One of my all time favorite features of pgsql. create tablespace is also non-transactable. ---------------------------(end of broadcast)--------------------------- TIP 5: don't forget to increase your free space map settings
