CREATE PROCEDURE usp_get_employees_by_salary_level(salary_level VARCHAR(7))
BEGIN
    SELECT e.first_name, e.last_name FROM employees AS e
    INNER JOIN (SELECT e.employee_id,e.salary,
     CASE WHEN e.salary < 30000 THEN 'Low'
          WHEN e.salary BETWEEN 30000 AND 50000 THEN 'Average'
            WHEN e.salary > 50000 THEN 'High'
            END
            AS 'salary_level' FROM employees AS e) AS sl
    ON e.employee_id = sl.employee_id
    WHERE salary_level = sl.salary_level
    ORDER BY e.first_name DESC, e.last_name DESC;
END