Triggers and Rules
In the previous chapter, we talked about server-side programming. In this chapter, we will use the concepts introduced in the previous chapter to manage the programming of events in PostgreSQL. The first thing we need to address is what an event in PostgreSQL actually is. In PostgreSQL, possible events are given by the SELECT/INSERT/UPDATE, and DELETE statements. There are also events related to data definition language (DDL) operations; however we will talk about those events in Chapter 17, Event Triggers.
In PostgreSQL, there are two ways to handle events:
- Rules
- Triggers
In this chapter, we will explore both of these ways and address when it is more appropriate to use one rather than the other. As a starting point, we can generally say that rules are usually simple event handlers, while triggers are more complex event handlers. Triggers and rules are often used to update accumulators and to modify or delete records that belong to...
