Получение информации о максимальной зарплате текущих сотрудников в каждом департаменте

CREATE TABLE `dept_emp` (
`emp_no` int(11) NOT NULL,
`dept_no` char(4) NOT NULL,
`from_date` date NOT NULL,
`to_date` date NOT NULL,
PRIMARY KEY (`emp_no`,`dept_no`)
);
CREATE TABLE `salaries` (
`emp_no` int(11) NOT NULL,
`salary` int(11) NOT NULL,
`from_date` date NOT NULL,
`to_date` date NOT NULL,
PRIMARY KEY (`emp_no`,`from_date`)
);

SELECT dept_no, s.emp_no, MAX(salary) AS salary FROM dept_emp de LEFT JOIN salaries s ON de.emp_no = s.emp_no WHERE de.to_date = '9999-01-01' AND s.to_date = '9999-01-01' GROUP BY dept_no

SELECT a.dept_no AS 'Департамент', a.emp_no AS 'Сотрудник', MAX(a.salary) AS 'Зарплата'
FROM (
    SELECT dp.dept_no, dp.emp_no, ss.salary 
    FROM dept_emp dp 
    LEFT JOIN salaries ss ON dp.emp_no = ss.emp_no 
    WHERE dp.to_date = '9999-01-01' AND ss.to_date = '9999-01-01'
) a
GROUP BY a.dept_no