SELECT k.dept_no, a.emp_no, a.salary, k.sal
  FROM salaries a,
      (SELECT b.dept_no, MAX(c.salary) sal
         FROM dept_emp b
        INNER JOIN salaries c
           ON b.emp_no = c.emp_no
        WHERE SYSDATE() BETWEEN c.from_date AND c.to_date
        GROUP BY 1
       ) k
WHERE a.salary = k.sal
ORDER BY 1;