CREATE OR REPLACE FUNCTION initialize_employee_statistics()
RETURNS TRIGGER
LANGUAGE plpgsql
AS $$
BEGIN
    /*
    * The employee is created first.
    * Work statistics can be initialized when
    * the employee is assigned to a store.
    * The actual store assignment should be handled
    * through works_in_store. */
    INSERT INTO worked (
        employee_id,
        total_working_hours,
        total_wage
    )
    VALUES (
        NEW.id,
        0,
        0
    );
    RETURN NEW;
END;
$$;

CREATE TRIGGER trg_initialize_employee_statistics
AFTER INSERT
ON employees
FOR EACH ROW
EXECUTE FUNCTION initialize_employee_statistics();