Book Image

MySQL 8 Cookbook

By : Karthik Appigatla
Book Image

MySQL 8 Cookbook

By: Karthik Appigatla

Overview of this book

MySQL is one of the most popular and widely used relational databases in the World today. The recently released MySQL 8 version promises to be better and more efficient than ever before. This book contains everything you need to know to be the go-to person in your organization when it comes to MySQL. Starting with a quick installation and configuration of your MySQL instance, the book quickly jumps into the querying aspects of MySQL. It shows you the newest improvements in MySQL 8 and gives you hands-on experience in managing high-transaction and real-time datasets. If you've already worked with MySQL before and are looking to migrate your application to MySQL 8, this book will also show you how to do that. The book also contains recipes on efficient MySQL administration, with tips on effective user management, data recovery, security, database monitoring, performance tuning, troubleshooting, and more. With quick solutions to common and not-so-common problems you might encounter while working with MySQL 8, the book contains practical tips and tricks to give you the edge over others in designing, developing, and administering your database effectively.
Table of Contents (20 chapters)
Title Page
Dedication
Packt Upsell
Contributors
Preface
Index

Descending index


Prior to MySQL 8, an index definition could contain the order (ascending or descending), but it was only parsed and not implemented. The index values were always stored in ascending order. MySQL 8.0 introduced support for descending indexes. Thus, the specified order in the index definition is not ignored. A descending index actually stores key values in descending order. Remember that scanning an ascending index in reverse is not efficient for a descending query.

Consider a case where, in a multi-column index, you can specify certain columns to be descending. This can help for queries wherein we have both ascending and descending ORDER BY clauses.

Suppose you want to sort the employees table with first_name ascending and last_name descending; MySQL cannot use the index on first_name and last_name. Without a descending index:

mysql> SHOW CREATE TABLE employees\G
*************************** 1. row ***************************
       Table: employees
Create Table: CREATE TABLE...