Chapter 9: Triggers
In this chapter, we’ll talk about another interesting feature in MySQL - triggers.
What is a Trigger?
A trigger is a series of actions that is activated when a defined event occurs for a specific table. This event can either be an INSERT, UPDATE or DELETE. Triggers can be invoked before or after the event.
To understand how triggers work, let’s look at an example.
We’ll use the employees table to demonstrate.
Suppose one of the employees has just resigned from the company and we want to delete this employee from the employees table. However, before we do that, we would like to transfer the data into another table called ex_employees as a form of back up. We can do this using a trigger.
Let’s first create an ...
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