Book Image

PostgreSQL Development Essentials

By : Baji Shaik
Book Image

PostgreSQL Development Essentials

By: 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
Credits
About the Authors
About the Reviewers
www.PacktPub.com
Preface

Introduction to triggers


A trigger is a specification that the database should run automatically whenever a certain type of operation is performed. It can be defined to run or fire either before or after any INSERT, UPDATE, or DELETE operation is performed on a particular object. This operation can be associated with a table, a view, a schema, or the database, and it is one of the following:

  • A Data Manipulation Language (DML) statement—DELETE, INSERT, or UPDATE

  • A Data Definition Language (DDL) statement—CREATE, ALTER, or DROP

  • A database operation—SERVERERROR, LOGON, LOGOFF, STARTUP, or SHUTDOWN

Like a stored procedure, a trigger can be invoked repeatedly. A procedure is explicitly run by a user or an application but triggers are implicitly fired when a triggering event occurs, no matter which user is connected or which application is used. It can be enabled and disabled but you cannot explicitly invoke it. While a trigger is enabled, the database automatically invokes it—that is, the trigger...