Book Image

Learn PostgreSQL - Second Edition

By : Luca Ferrari, Enrico Pirozzi
1 (2)
Book Image

Learn PostgreSQL - Second Edition

1 (2)
By: Luca Ferrari, Enrico Pirozzi

Overview of this book

The latest edition of this PostgreSQL book will help you to start using PostgreSQL from absolute scratch, helping you to quickly understand the internal workings of the database. With a structured approach and practical examples, go on a journey that covers the basics, from SQL statements and how to run server-side programs, to configuring, managing, securing, and optimizing database performance. This new edition will not only help you get to grips with all the recent changes within the PostgreSQL ecosystem but will also dig deeper into concepts like partitioning and replication with a fresh set of examples. The book is also equipped with Docker images for each chapter which makes the learning experience faster and easier. Starting with the absolute basics of databases, the book sails through to advanced concepts like window functions, logging, auditing, extending the database, configuration, partitioning, and replication. It will also help you seamlessly migrate your existing database system to PostgreSQL and contains a dedicated chapter on disaster recovery. Each chapter ends with practice questions to test your learning at regular intervals. By the end of this book, you will be able to install, configure, manage, and develop applications against a PostgreSQL database.
Table of Contents (22 chapters)
20
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21
Index

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...