Book Image

Learn PostgreSQL

By : Luca Ferrari, Enrico Pirozzi
Book Image

Learn PostgreSQL

By: Luca Ferrari, Enrico Pirozzi

Overview of this book

PostgreSQL is one of the fastest-growing open source object-relational database management systems (DBMS) in the world. As well as being easy to use, it’s scalable and highly efficient. In this book, you’ll explore PostgreSQL 12 and 13 and learn how to build database solutions using it. Complete with hands-on tutorials, this guide will teach you how to achieve the right database design required for a reliable environment. You'll learn how to install and configure a PostgreSQL server and even manage users and connections. The book then progresses to key concepts of relational databases, before taking you through the Data Definition Language (DDL) and commonly used DDL commands. To build on your skills, you’ll understand how to interact with the live cluster, create database objects, and use tools to connect to the live cluster. You’ll then get to grips with creating tables, building indexes, and designing your database schema. Later, you'll explore the Data Manipulation Language (DML) and server-side programming capabilities of PostgreSQL using PL/pgSQL, before learning how to monitor, test, and troubleshoot your database application to ensure high-performance and reliability. By the end of this book, you'll be well-versed with the Postgres database and be able to set up your own PostgreSQL instance and use it to build robust solutions.
Table of Contents (27 chapters)
Section 1: Getting Started
Section 2: Interacting with the Database
Section 3: Administering the Cluster
Section 4: Replication
Section 5: The PostegreSQL Ecosystem

Exploring CTEs

In this section, we are going to talk about CTEs. This section will be split into three parts. Firstly, we will talk about the concept of CTEs; secondly, we will discuss how CTEs are implemented in PostgreSQL 12; and finally, we will explore some examples of how to use CTEs.

CTE concept

A CTE, or a common table expression, is a temporary result taken from a SQL statement. This statement can contain SELECT, INSERT, UPDATE, or DELETE instructions. The lifetime of a CTE is equal to the lifetime of the query. Here is an example of a CTE definition:

WITH cte_name (column_list) AS (

If, for example, we wanted to create a temporary dataset with all the posts written by the author scotty, we would have to write this:

forumdb=# with posts_author_1 as 
(select p.* from posts p
inner join users u on
where username='scotty')
select pk,title from posts_author_1;
pk | title
4 | Re:my orange
5 | my tomato