- Triggers are SQL operations executed automatically in response to a particular event
- These events are:
- Trigger syntax varies by SQL dialect. In MySQL, BEGIN ... END is needed for a trigger containing several statements; it is optional for a single statement.
- Supported trigger targets vary by dialect. MySQL triggers belong to permanent tables and cannot be attached to a view.
Examples of useful triggers include:
- When a customer is added, check that a phone number is provided and the postal code meets the requirements
- When a product is ordered, reduce stock by the quantity ordered
- Before a row is deleted, copy it into an archive table