SELECT e.dept_no,
    e.emp_no,
    e.salary
FROM(
    SELECT  de.dept_no,
    de.emp_no,
    s.salary,
    DENSE_RANK() OVER(PARTITION BY de.dept_no ORDER BY s.salary DESC) rk
    FROM dept_emp de
    JOIN salaries s USING(emp_no)
) e

WHERE e.rk = 1
ORDER BY e.dept_no