In SQL, the concept of foreign keys is an important one that can be found in all professional databases used in the industry. The core idea is to prevent your PostgreSQL database from storing inconsistent data by enforcing constraints ensuring the correctness of your tables (at least as far as relations between objects are concerned). […]

  Sometimes you want to enforce a condition on a table that cannot be implemented by a constraint. In such a case it is tempting to use triggers instead. This article describes how to do this and what to watch out for. It will also familiarize you with the little-known PostgreSQL feature of “constraint triggers”. […]