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)
1
Section 1: Getting Started
5
Section 2: Interacting with the Database
12
Section 3: Administering the Cluster
20
Section 4: Replication
23
Section 5: The PostegreSQL Ecosystem

Using advanced statement window functions

In this section, we will discuss advanced window functions in more detail, and we will explore some techniques that may be useful for carrying out more detailed data analysis.

Let's start with another way to write the same aggregate that we have described before:

forumdb=# select distinct category, count(*) over w1 
from posts
WINDOW w1 as (partition by category RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW)
order by category;
category | count
----------+-------
12 | 1
10 | 1
11 | 3
(3 rows)

What does RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW mean? They are the default conditions, known as the frame clause. This means that the data is partitioned, first by category, and then within the partition, the count is calculated by resetting the count every time the frame is changed.

The frame clause

In this section, we'll talk about the frame clause, which allows us to manage partitions in a different way. The frame...