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you can use setup a foreign key constraint in your create table so that column is only populated when there is a value which syncs to the referenced value http://www.postgresql.org/docs/7.4/interactive/sql-createtable.html Martin ______________________________________________ Disclaimer and confidentiality note Everything in this e-mail and any attachments relates to the official business of Sender. This transmission is of a confidential nature and Sender does not endorse distribution to any party other than intended recipient. Sender does not necessarily endorse content contained within this transmission. > To: pgsql-general@xxxxxxxxxxxxxx > From: matt@xxxxxxxxxx > Subject: [GENERAL] Foreign Key normalization question > Date: Tue, 2 Sep 2008 19:14:17 +0000 > > I'm building an app that has a customers table, a locations table, a > products table, and a product_locations table. > > They make a diamond shape. > > The locations table and the products table each have a customer_id > column that links back to the customers table. > > Then the product_locations table table has just two columns: a > location_id column and a product_id column, each linking back to the > appropriate table. > > I want to write a constraint or a trigger or something else that makes > sure that before a (location_id, product_id) tuple is inserted into the > product_locations table, the system verifies that the product links to > the same customer as the location. > > How do I do this? > > Thanks in advance. > > Matt > > > > -- > Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-general Get thousands of games on your PC, your mobile phone, and the web with Windows®. Game with Windows |
