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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Index

Managing triggers in PostgreSQL

In the previous section, we talked about rules. In this section, we will talk about triggers, what they are, and how to use them. We need to start by understanding what triggers are; if we understand what rules are, this should be simple. In the previous section, we defined rules as simple event handlers; now we can define triggers as complex event handlers. For triggers, as for rules, there are NEW and OLD records, which assume the same meaning for triggers as they did for rules. For triggers, the manageable events are INSERT/DELETE/UPDATE and TRUNCATE. Another difference between rules and triggers is that with triggers, it is possible to handle INSERT/UPDATE/DELETE and TRUNCATE events before they happen or after they have happened. With triggers, we can also use the INSTEAD OF option, but only on views.

So, we can manage the following events:

  • BEFORE INSERT/UPDATE/DELETE/TRUNCATE
  • AFTER INSERT/UPDATE/DELETE/TRUNCATE
  • INSTEAD...