How many Triggers are possible in MySQL?

In MySQL, each table can have up to six triggers, namely:

1. BEFORE INSERT: A trigger that fires before inserting new records.
2. AFTER INSERT: A trigger that fires after inserting new records.
3. BEFORE UPDATE: A trigger that fires before updating existing records.
4. AFTER UPDATE: A trigger that fires after updating existing records.
5. BEFORE DELETE: A trigger that fires before deleting existing records.
6. AFTER DELETE: A trigger that fires after deleting existing records.

Each trigger type is defined for specific operations to ensure that specific logic is executed before and after data modifications. These triggers can help maintain data integrity, automate specific tasks, or execute complex business logic.

Suppose there is an order system with a table called orders; the following triggers can be set for this table:

• BEFORE INSERT trigger can be used to validate new order data, such as checking if the order amount is reasonable.
• AFTER INSERT trigger can be used to automatically update inventory quantities or send order confirmation emails to customers.
• BEFORE UPDATE trigger can be used to verify that updates to the order status comply with business rules, such as preventing cancellation of shipped orders.
• AFTER UPDATE trigger can be used to record the history of changes to the order status.
• BEFORE DELETE trigger can be used to prevent accidental deletion of important order records.
• AFTER DELETE trigger can be used to clean up related data, such as order details.

Using these triggers ensures consistency in business logic and reduces the burden on the application layer.