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Learn PostgreSQL

Learn PostgreSQL - Second Edition

By : Ferrari, Enrico Pirozzi
4.4 (33)
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Learn PostgreSQL

Learn PostgreSQL

4.4 (33)
By: Ferrari, Enrico Pirozzi

Overview of this book

The latest edition of this PostgreSQL book will help you to start using PostgreSQL from absolute scratch, helping you to quickly understand the internal workings of the database. With a structured approach and practical examples, go on a journey that covers the basics, from SQL statements and how to run server-side programs, to configuring, managing, securing, and optimizing database performance. This new edition will not only help you get to grips with all the recent changes within the PostgreSQL ecosystem but will also dig deeper into concepts like partitioning and replication with a fresh set of examples. The book is also equipped with Docker images for each chapter which makes the learning experience faster and easier. Starting with the absolute basics of databases, the book sails through to advanced concepts like window functions, logging, auditing, extending the database, configuration, partitioning, and replication. It will also help you seamlessly migrate your existing database system to PostgreSQL and contains a dedicated chapter on disaster recovery. Each chapter ends with practice questions to test your learning at regular intervals. By the end of this book, you will be able to install, configure, manage, and develop applications against a PostgreSQL database.
Table of Contents (22 chapters)
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20
Other Books You May Enjoy
21
Index

Using basic statement window functions

As we saw in the previous chapter, aggregation functions behave in the following way:

Chart  Description automatically generated

Figure 6.1: Standard group by aggregation

The data is first sorted and then aggregated; the data is then flattened through aggregation. This is what happens when we execute the following statement, after connecting as the forum user to forumdb database:

forumdb=> select category,count(*) from posts group by category order by category;
 category | count
----------+-------
        1 |     2
        3 |     1
(2 rows)

Alternatively, we can decide to use window functions by executing the following statement:

forumdb=> select category, count(*) over (partition by category) from posts order by category;
 category | count
----------+-------
        1 |     2
        1 |     2
        3 |     1
(3 rows)

Window functions create aggregates without flattening the data into a single row. However, they replicate it for all the rows to...

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