**Course Title:** SQLite Mastery: Lightweight Database Management **Section Title:** Views, Triggers, and Advanced Features **Topic:** Introduction to Triggers and Their Use Cases **What are Triggers?** In SQLite, triggers are a type of procedural logic that can be used to enforce data integrity and automate actions on data changes. Triggers are stored in the database and are executed automatically when a specific event occurs. **Types of Triggers** There are three types of triggers in SQLite: * **BEFORE trigger:** This type of trigger is executed before the event that fires the trigger occurs. For example, if we create a before trigger for an insert statement, it would be executed before the new data is inserted into the table. * **AFTER trigger:** This type of trigger is executed after the event that fires the trigger occurs. For example, if we create an after trigger for an insert statement, it would be executed after the new data has been inserted into the table. * **INSTEAD OF trigger:** This type of trigger can only be used on views. It is executed instead of the event that fires the trigger. For example, if we create an instead of trigger for an insert statement on a view, the insert operation would not be executed on the underlying table. **Trigger Syntax** The basic syntax for creating a trigger in SQLite is as follows: ```sql CREATE TRIGGER trigger_name BEFORE/AFTER/INSTEAD OF event ON table_name FOR EACH ROW/STATEMENT BEGIN -- Code to be executed by the trigger END; ``` Here is a breakdown of the syntax: * `CREATE TRIGGER`: This is the keyword used to create a new trigger. * `trigger_name`: This is the name of the trigger. * `BEFORE/AFTER/INSTEAD OF`: This specifies the type of trigger. * `event`: This specifies the event that fires the trigger. Can be one of the following: `INSERT`, `DELETE`, `UPDATE`. * `ON table_name`: This specifies the table that the trigger is attached to. * `FOR EACH ROW/STATEMENT`: This specifies whether the trigger is executed for each row affected by the event, or only once for the entire event. * `BEGIN...END;`: This is the block of code that is executed by the trigger. **Trigger Example** Here is an example of a trigger that adds a "date_modified" column with the current date and time when any row in a table is updated: ```sql CREATE TABLE orders ( id INTEGER PRIMARY KEY, customer_name TEXT NOT NULL, date_modified TEXT ); CREATE TRIGGER tr_orders_update BEFORE UPDATE ON orders FOR EACH ROW BEGIN NEW.date_modified = DATETIME('NOW'); END; INSERT INTO orders (id, customer_name) VALUES (1, 'John Doe', NULL); UPDATE orders SET customer_name = 'Jane Smith' WHERE id = 1; ``` **Advantages and Disadvantages of Triggers** **Advantages:** * Can be used to enforce complex data integrity rules * Can be used to automate repetitive tasks * Can be used to generate reports **Disadvantages:** * Can affect database performance * Can be difficult to debug * Can be used to circumvent database security **Conclusion** Triggers are a powerful feature in SQLite that can be used to automate actions on data changes and enforce data integrity. By understanding the different types of triggers and how to use them, you can write more efficient and secure database code. In the next topic, we will learn how to use triggers to automate actions on data changes. **We Appreciate Your Thoughts** What do you think about this topic? Did this explanation of SQLite triggers help clarify things for you? Is there something we missed, or an advanced SQLite topic you would like us to explain or clarify for you? How can we provide better content? Let us know in a comment.