What is a Database Trigger?
A database trigger, or DB trigger, is a database object that is associated with a specific table or view and is activated automatically when a certain event or action occurs on that table or view. Triggers are used to monitor and respond to changes in data, providing a way to automate data manipulation tasks.
Basic Concepts of Database Triggers
- Event or Action: Triggers are triggered by specific events or actions that occur on the associated table or view. These can include INSERT, UPDATE, or DELETE operations.
- Trigger Timing: Triggers can be classified into two types based on their timing of execution:
- Before Triggers: These triggers are executed before the associated event or action takes place. They can be used to validate data or modify the values of the changes being made.
- After Triggers: These triggers are executed after the associated event or action has been completed. They are commonly used to perform additional actions such as logging, auditing, or updating other tables based on the changes made.
- Triggering Statement: Triggers are associated with specific SQL statements, such as INSERT, UPDATE, or DELETE. They are executed when these statements are executed on the associated table or view.
- Trigger Body: The trigger body contains the code or actions that need to be executed when the trigger is triggered. This can include SQL statements, PL/SQL code, or calls to stored procedures or functions.
- Triggered Action: The action or actions performed by the trigger when it is triggered. This can include modifying data, performing calculations, or invoking other business logic.
By using triggers, database administrators and developers can monitor and automate data manipulation tasks efficiently. Triggers enable the implementation of complex business rules and help maintain data integrity and consistency.