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

Exclusion constraints

This constraint specifies that if any two rows are compared on the specified column(s) or expression(s) using the specified operator(s), at least one of these operator comparisons will return false or null. Let's look at this example:

name varchar,
age integer,
(AGE WITH <>));

In the preceding example, we are enforcing that age has to match an already existing one. What happens if you try to insert a different age? Let's look at this example:

postgres=# INSERT INTO example VALUES ('scott', '26');
postgres=# INSERT INTO example VALUES ('scott', '27');
ERROR:  conflicting key value violates exclusion constraint  "example_age_excl"
DETAIL:  Key (age)=(27) conflicts with existing key (age)=(26).

It throws an ERROR that the exclusion constraint is violated. Adding an exclusion constraint will automatically create an index of the type specified in the constraint declaration.