SELECT COUNT(*) AS `Rows`, UserID
FROM `postings`
GROUP BY UserID
ORDER BY `Rows` DESC
LIMIT 1

SELECT COUNT(*) AS `Rows`, UserID
FROM `postings`
GROUP BY UserID
ORDER BY `Rows` DESC
LIMIT 1

SELECT user_id, COUNT(*) FROM postings ORDER BY COUNT(*) GROUP BY user_id LIMIT 1

select user_id, count(*) as posts
from postings
group by user_id
having count(*) = max(count(*)) ;