Book Image

PostgreSQL Administration Cookbook, 9.5/9.6 Edition - Third Edition

Book Image

PostgreSQL Administration Cookbook, 9.5/9.6 Edition - Third Edition

Overview of this book

PostgreSQL is a powerful opensource database management system; now recognized as the expert's choice for a wide range of applications, it has an enviable reputation for performance and stability. PostgreSQL provides an integrated feature set comprising relational database features, object-relational, text search, Geographical Info Systems, analytical tools for big data and JSON/XML document management. Starting with short and simple recipes, you will soon dive into core features, such as configuration, server control, tables, and data. You will tackle a variety of problems a database administrator usually encounters, from creating tables to managing views, from improving performance to securing your database, and from using monitoring tools to using storage engines. Recipes based on important topics such as high availability, concurrency, replication, backup and recovery, as well as diagnostics and troubleshooting are also given special importance. By the end of this book, you will have all the knowledge you need to run, manage, and maintain PostgreSQL efficiently.
Table of Contents (13 chapters)

Adding/removing columns on a table

As designs change, we may want to add or remove columns from our data tables. These are common operations in development, though they need more careful planning on a running production database server, as they take full locks and may run for long periods.

How to do it...

You can add a new column to a table using this command:

ALTER TABLE mytable
ADD COLUMN last_update_timestamp TIMESTAMP WITHOUT TIME ZONE;

You can drop the same column using the following command:

ALTER TABLE mytable
DROP COLUMN last_update_timestamp;

You can combine multiple operations when using ALTER TABLE, which then applies the changes in a sequence. This allows you to do a useful trick, which is to add a column unconditionally...