1. Introduction

In this tutorial, we will delve into the realm of SQL triggers, which are special stored procedures that execute automatically based on certain events. Our key focus will be on how to define a trigger, specify the event that fires it, and manage existing triggers.

By the end of this tutorial, you will be able to:
- Understand what triggers are and their importance
- Create and define triggers
- Manage and modify existing triggers

Prerequisites:
Basic understanding of SQL, including CRUD operations (Create, Read, Update, Delete) and some familiarity with SQL stored procedures.

2. Step-by-Step Guide

Triggers are database operations that are automatically performed when a specified database event occurs. These events can be an insert, update, or delete operation.

Triggers are useful for enforcing complex business rules or for automating certain operations.

The basic syntax for creating a trigger is:

CREATE TRIGGER trigger_name
[BEFORE | AFTER] event_name
ON table_name FOR EACH ROW
BEGIN
    -- Trigger logic goes here
END;

3. Code Examples

Let's create a simple trigger that logs changes to a 'users' table.

Example 1: Creation of a Trigger

CREATE TRIGGER user_changes
AFTER UPDATE
ON users FOR EACH ROW
BEGIN
   INSERT INTO logs(old_data, new_data, timestamp)
   VALUES (OLD.*, NEW.*, NOW());
END;

In this example, a trigger named user_changes is created. It is set to execute after any UPDATE operation on the 'users' table. The trigger inserts the old and new data into a 'logs' table.

Example 2: Managing Triggers

You can view all triggers in your database with the following command:

SHOW TRIGGERS;

To delete a trigger, use the DROP TRIGGER statement:

DROP TRIGGER IF EXISTS user_changes;

This will delete the user_changes trigger if it exists.

4. Summary

In this tutorial, we've learned what SQL triggers are, how to create them, and how to manage them. Triggers are a powerful tool that can help enforce business rules and automate tasks.

For further learning, you can explore more complex triggers, and how to use them with different data types and SQL operations.

5. Practice Exercises

Exercise 1: Create a trigger that deletes a row from a 'logs' table whenever a row in 'users' table is deleted.

Exercise 2: Create a trigger that prevents a row from being inserted into a 'users' table if the 'username' already exists.

Exercise 3: Create a trigger that updates a 'last_modified' column in 'users' table whenever a row is updated.

Remember, practice is the key to mastering any concept. Happy coding!