instruction: Longest Average Poster (ie., avg length of Q&A's).
response: SELECT OwnerUserId, COUNT(Id) AS "numposts", AVG(LENGTH(Body)) AS "avglength" FROM Posts WHERE PostTypeId IN (1, 2) AND YEAR(CreationDate) >= 2018 GROUP BY OwnerUserId HAVING COUNT(Id) > 10 ORDER BY AVG(LENGTH(Body)) DESC