/*the more we work the bigger is the salary?*/

SELECT workhours, ROUND(high_salary*1.0/low_salary, 1) AS high_to_low_ratio FROM
(SELECT CASE WHEN workinhoursperweek BETWEEN 0 AND 12 THEN 'quarter'
            WHEN workinhoursperweek BETWEEN 12 AND 24 THEN 'half'
            WHEN workinhoursperweek BETWEEN 24 AND 48 THEN 'full'
            WHEN workinhoursperweek BETWEEN 48 AND 96 THEN 'double'
  END AS workhours,
    SUM (CASE WHEN salarylevel = '>50K' THEN 1 ELSE 0 END) high_salary,
    SUM (CASE WHEN salarylevel = '<=50K' THEN 1 ELSE 0 END) low_salary
FROM person
GROUP BY  workhours) tbl 
ORDER BY 2 DESC;