table inside table

SELECT x.DEPARTMENT_ID, e1.FIRST_NAME, x.mn, x.mx
FROM ( SELECT e2.DEPARTMENT_ID, MAX(e2.SALARY) AS mn, MIN(e2.SALARY) as mx
      FROM employees e2 GROUP BY e2.DEPARTMENT_ID ) as x
      JOIN employees e1 ON e1.DEPARTMENT_ID = x.DEPARTMENT_ID