Book Image

Learn PostgreSQL

By : Luca Ferrari, Enrico Pirozzi
Book Image

Learn PostgreSQL

By: Luca Ferrari, Enrico Pirozzi

Overview of this book

PostgreSQL is one of the fastest-growing open source object-relational database management systems (DBMS) in the world. As well as being easy to use, it’s scalable and highly efficient. In this book, you’ll explore PostgreSQL 12 and 13 and learn how to build database solutions using it. Complete with hands-on tutorials, this guide will teach you how to achieve the right database design required for a reliable environment. You'll learn how to install and configure a PostgreSQL server and even manage users and connections. The book then progresses to key concepts of relational databases, before taking you through the Data Definition Language (DDL) and commonly used DDL commands. To build on your skills, you’ll understand how to interact with the live cluster, create database objects, and use tools to connect to the live cluster. You’ll then get to grips with creating tables, building indexes, and designing your database schema. Later, you'll explore the Data Manipulation Language (DML) and server-side programming capabilities of PostgreSQL using PL/pgSQL, before learning how to monitor, test, and troubleshoot your database application to ensure high-performance and reliability. By the end of this book, you'll be well-versed with the Postgres database and be able to set up your own PostgreSQL instance and use it to build robust solutions.
Table of Contents (27 chapters)
Section 1: Getting Started
Section 2: Interacting with the Database
Section 3: Administering the Cluster
Section 4: Replication
Section 5: The PostegreSQL Ecosystem

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 have understood 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: