/*produces counts for each gain group per occupation*/
SELECT ifnull(occupation,'N/A') AS occupation, 
  SUM(CASE WHEN capitalgain BETWEEN 0 AND 33000 THEN 1 else 0 END) 'Q3_count',
  SUM(CASE WHEN capitalgain BETWEEN 33000 AND 66000 THEN 1 else 0 END) 'Q2_count',
  SUM(CASE WHEN capitalgain >66000 THEN 1 else 0 END) 'Q1_count'
FROM person
GROUP BY occupation
ORDER BY 1;