PostgreSQL, Second Edition

Triggers

So far, all the functions that defined in this chapter have been called explicitly, either by using a SELECT function() command or by using the function within an expression. You can also call certain PL/pgSQL functions automatically. A trigger is a function that is called whenever a specific event occurs in a given table. An INSERT command, an UPDATE command, or a DELETE command can cause a trigger to execute.

Let's look at a simple example. You currently have a customers table defined like this:

CREATE TABLE customers 
(
      customer_id    integer primary key,
      customer_name  character varying(50) not null,
      phone          character(8),
      birth_date     date,
      balance        decimal(7,2)
);

You want to create a new table that you can use to archive any rows that ...