Triggers are database objects that are automatically executed when certain events occur. Triggers can be used to enforce complex business rules, perform data validation, or perform other actions SQLite cannot do directly.
Triggers are written in SQL, and can be attached to
views. When an event that the trigger is programmed to respond to occurs, the SQL code in the trigger is executed.
There are four types of SQLite triggers:
- BEFORE INSERT
- AFTER INSERT
- BEFORE UPDATE
- AFTER UPDATE
BEFORE INSERT and
AFTER INSERT triggers are fired before or after a new row is inserted into the table.
BEFORE UPDATE and
AFTER UPDATE triggers are fired before or after an existing row in the table or view is updated.
Triggers can be useful for a variety of tasks, such as:
- Enforcing complex business rules
- Performing data validation
- Auditing changes to data
- Generating derived column values
- Modifying incoming data to conform to a specific format
To use triggers, you first need to create them using the
CREATE TRIGGER statement. This statement specifies the name of the trigger, the SQL code to execute when the trigger fires, and the conditions under which the trigger should fire.
Once a trigger has been created, it will be executed automatically whenever the conditions for that trigger are met.
To delete a trigger from the
SQLite database, use the
DROP TRIGGER statement.
SQLite triggers are a powerful tool that can be used to enforce complex business rules, perform data validation, or perform other actions SQLite cannot do directly. With SQLite triggers, you can make your SQLite database even more flexible and powerful.