Book Image

Learn PostgreSQL - Second Edition

By : Luca Ferrari, Enrico Pirozzi
1 (2)
Book Image

Learn PostgreSQL - Second Edition

1 (2)
By: Luca 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)
20
Other Books You May Enjoy
21
Index

Using limit and offset

The limit clause is the PostgreSQL way to limit the number of rows returned by a query, whereas the offset clause is used to skip a specific number of rows returned by the query.

limit and offset are used to return a portion of data from a resultset generated by a query; the limit clause is used to limit the number of records in output and the offset clause is used to provide PostgreSQL with the position in the resultset from which to start returning data.

They can be used independently or together.

Now let’s test limit and offset using the following queries:

forumdb=> select * from categories order by pk limit 1;
 pk |  title   |         description     
----+----------+------------------------------
  1 | Database | Database related discussions
(1 row)

The preceding query returns only the first record that we have inserted; this is because the pk field is an integer type with a default value generated always as the identity.

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