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

Triggers


A trigger is used to activate something before or after the trigger event. For example, you can have a trigger activate before each row that is inserted into a table or after each row that is updated.

Triggers are highly useful while altering a table without downtime (Refer to Chapter 10, Table Maintenance, in the Alter table using online schema change tool section) and also for auditing purposes. Suppose you want to find out the previous value of a row, you can write a trigger that saves those rows in another table before updating. The other table serves as an audit table that has the previous records.

The trigger action time can be BEFORE or AFTER, which indicates whether the trigger activates before or after each row to be modified.

Trigger events can be INSERT, DELETE, or UPDATE:

  • INSERT: Whenever a new row gets inserted through INSERTREPLACE, or LOAD DATA, the trigger gets activated
  • UPDATE: Through the UPDATE statement
  • DELETE: Through the DELETE or REPLACE statements

From MySQL 5...