SQLite is a popular lightweight and embedded relational database management system that offers support for triggers and stored procedures. Triggers and stored procedures are powerful features that enhance the functionality and control of the database.

Triggers

A trigger is a database object that is automatically executed in response to a specific event or action that occurs on a table, such as an insert, update, or delete operation. Triggers can be used to enforce business rules, perform validations, log changes, or trigger other actions.

To create a trigger in SQLite, you can use the CREATE TRIGGER statement. Here’s an example of a trigger that logs all the changes made to a specific table:

CREATE TRIGGER log_changes
AFTER UPDATE ON employees
FOR EACH ROW
BEGIN
    INSERT INTO changes (table_name, change_date, operation)
    VALUES ('employees', datetime('now'), 'update');
END;

In this example, whenever an update operation is performed on the employees table, the trigger log_changes is executed. It logs the table name, the current date and time, and the operation performed into the changes table.

Triggers in SQLite support various events such as AFTER INSERT, BEFORE UPDATE, or AFTER DELETE. You can also specify the trigger firing time as FOR EACH ROW or FOR EACH STATEMENT depending on whether you want the trigger to execute for each row affected by the operation or only once for the whole statement.

Stored Procedures

Stored procedures are precompiled database objects stored in the database that can be called to perform a specific task or set of tasks. They can accept parameters and return values, making them ideal for encapsulating complex logic and promoting code reusability.

SQLite supports stored procedures using user-defined functions (UDFs). You can define UDFs in different programming languages such as C, Python, or Lua. Here’s an example of a stored procedure written in Python:

import sqlite3

def my_stored_procedure(param1, param2):
    # Perform some tasks
    
    # Return a result
    return result

# Register the stored procedure with SQLite
conn = sqlite3.connect('mydatabase.db')
conn.create_function('my_stored_procedure', 2, my_stored_procedure)

In this example, we define a stored procedure called my_stored_procedure that takes two parameters and returns a result. We then register this stored procedure with SQLite using the create_function method.

Once registered, you can call the stored procedure from your SQL statements, just like any other built-in function. For example:

SELECT my_stored_procedure('param1', 'param2');

Conclusion

Triggers and stored procedures offer additional flexibility and control in SQLite databases. Triggers allow you to automate actions based on specific events, while stored procedures provide a way to encapsulate and reuse complex functionality. Understanding and utilizing these features can greatly enhance the capabilities of your SQLite database.

[References: SQLite Documentation, Link to SQLite documentation]