SELECT u.display_name,
       COUNT(ps.user_id) AS cnt
FROM stackoverflow.posts AS p
LEFT OUTER JOIN stackoverflow.users AS u ON p.user_id = u.id
LEFT OUTER JOIN stackoverflow.post_types AS pt ON p.post_type_id = pt.id
LEFT OUTER JOIN stackoverflow.posts AS ps ON p.parent_id = ps.id
WHERE pt.type = 'Answer'
  AND p.creation_date <= u.creation_date + INTERVAL '1 months'
GROUP BY u.display_name
HAVING COUNT(p.id) > 100
ORDER BY u.display_name ASC;