SELECT
  dept_id,
  PERCENTILE_CONT(0.5) WITHIN GROUP (ORDER BY salary) AS median_salary,
  PERCENTILE_CONT(0.25) WITHIN GROUP (ORDER BY salary) AS p25_salary,
  PERCENTILE_CONT(0.75) WITHIN GROUP (ORDER BY salary) AS p75_salary
FROM employees
GROUP BY dept_id
ORDER BY dept_id;