Book Image

Learning PostgreSQL 10 - Second Edition

Book Image

Learning PostgreSQL 10 - Second Edition

Overview of this book

PostgreSQL is one of the most popular open source databases in the world, supporting the most advanced features included in SQL standards. This book will familiarize you with the latest features released in PostgreSQL 10. We’ll start with a thorough introduction to PostgreSQL and the new features introduced in PostgreSQL 10. We’ll cover the Data Definition Language (DDL) with an emphasis on PostgreSQL, and the common DDL commands supported by ANSI SQL. You’ll learn to create tables, define integrity constraints, build indexes, and set up views and other schema objects. Moving on, we’ll cover the concepts of Data Manipulation Language (DML) and PostgreSQL server-side programming capabilities using PL/pgSQL. We’ll also explore the NoSQL capabilities of PostgreSQL and connect to your PostgreSQL database to manipulate data objects. By the end of this book, you’ll have a thorough understanding of the basics of PostgreSQL 10 and will have the necessary skills to build efficient database solutions.
Table of Contents (23 chapters)
Title Page
Credits
About the Authors
About the Reviewers
www.PacktPub.com
Customer Feedback
Preface

Arrays


An array is a data structure consisting of a collection of elements (values or variables), the order of the elements in the array is significant and each element in the array is identified by an index. The index of the the array is often started by 1, but in some programming languages such as C and C++, the index starts at 0. Array elements should have the same type such as INT or TEXT. 

Multidimensional arrays are supported; here, the array type can be a base, enum, or composite type. Array elements should have only one data type. PostgreSQL arrays allow duplicate values as well as null values. The following example shows how to initialize a one-dimensional array and get the first element:

car_portal=> SELECT ('{red, green, blue}'::text[])[1] as red ;
 red 
-----
 red
(1 row)

The array length, by default, is not bound to a certain value, but this can also be specified when using arrays to define a relation. By default, an array index, as shown in the preceding example, starts from...