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

Conversion between datatypes

Like other languages, PostgreSQL has one of the significant features, that is, conversion of datatypes. Many times, we will need to convert between datatypes in a database. Type conversions are very useful, and sometimes necessary, while running queries. For example, we are trying to import data from another system and the target-column datatype is different from the source-column datatype; we can use the conversion feature of PostgreSQL to implement runtime conversions between compatible datatypes using CAST functions. The following is the syntax:

CAST ( expression AS type ) 


expression :: type 

This contains a column name or a literal for which you want to convert the datatype. Converting null values returns nulls. The expression cannot contain blank or empty strings. The type-datatype to which you want to convert the expression.

Let's consider an example of an order table where we want to change the date type to a character.

SELECT cast(ordered_date...