WITH l AS (SELECT u.id AS user_id,
u.display_name
FROM stackoverflow.posts AS p
JOIN stackoverflow.users AS u ON p.user_id = u.id
JOIN stackoverflow.post_types AS pt ON p.post_type_id = pt.id
WHERE pt.type = 'Answer'
AND CAST(p.creation_date as date ) BETWEEN CAST(u.creation_date as date) AND CAST(u.creation_date as date) + interval '1 month'
)

SELECT display_name,
COUNT(DISTINCT user_id)
FROM l
GROUP BY 1
HAVING COUNT(*) > 100
ORDER BY 1