Book Image

PostgreSQL Development Essentials

By : Manpreet Kaur, Baji Shaik
Book Image

PostgreSQL Development Essentials

By: Manpreet Kaur, Baji Shaik

Overview of this book

PostgreSQL is the most advanced open source database in the world. It is easy to install, configure, and maintain by following the documentation; however, it’s difficult to develop applications using programming languages and design databases accordingly. This book is what you need to get the most out of PostgreSQL You will begin with advanced SQL topics such as views, materialized views, and cursors, and learn about performing data type conversions. You will then perform trigger operations and use trigger functions in PostgreSQL. Next we walk through data modeling, normalization concepts, and the effect of transactions and locking on the database. The next half of the book covers the types of indexes, constrains, and the concepts of table partitioning, as well as the different mechanisms and approaches available to write efficient queries or code. Later, we explore PostgreSQL Extensions and Large Object Support in PostgreSQL. Finally, you will perform database operations in PostgreSQL using PHP and Java. By the end of this book, you will have mastered all the aspects of PostgreSQL development. You will be able to build efficient enterprise-grade applications with PostgreSQL by making use of these concepts
Table of Contents (17 chapters)
PostgreSQL Development Essentials
About the Authors
About the Reviewers

Creating a trigger function

PL/pgSQL allows us to make a trigger function. This trigger function is similar to an ordinary function but it does not have any parameter and has a return type trigger. A trigger fires when a condition is met and executes a special type of stored procedure called a trigger function.

PostgreSQL will call a trigger function when changes are being made to a particular table. The function must either return NULL or a row that matches the structure of the table for which the trigger function has been called.

As mentioned earlier, the trigger function is created as an ordinary function. The following is the syntax to create this:

CREATE FUNCTION trigger_function() RETURN trigger AS

The trigger function receives data about their calling environment through a special structure called TriggerData, which contains a set of local variables. For example, OLD and NEW represent the states of a row in the table before or after the triggering event. PostgreSQL provides other local...