Introduction to MySQL Triggers | Nettuts+
MySQL triggers are database rules that automatically execute additional operations when data is inserted, updated, or deleted, allowing developers to handle data integrity, logging, and business logic at the database layer rather than in application code. The article demonstrates three practical applications: maintaining referential integrity by automatically deleting related records, auditing changes by logging modifications to separate tables, and enforcing business rules like automatic price calculations based on cost updates. While triggers add modest performance overhead to individual queries, they reduce overall latency by eliminating multiple round trips to the database and move critical data logic away from the application layer where it's easier to enforce consistently.