instruction: A list of the top 20 users with the highest average answer score excluding
  community wiki / closed posts or users with less than 10 answers. A list of the top 500 users with the highest average answer score excluding
  community wiki / closed posts or users with less than 10 answers
response: SELECT Users.Id AS "user_link", COUNT(Posts.Id) AS Answers, CAST(AVG(CAST(Score AS FLOAT)) AS FLOAT(6, 2)) AS "average_answer_score" FROM Posts INNER JOIN Users ON Users.Id = OwnerUserId WHERE PostTypeId = 2 AND CommunityOwnedDate IS NULL AND ClosedDate IS NULL GROUP BY Users.Id, DisplayName HAVING COUNT(Posts.Id) > 10 ORDER BY 'average_answer_score' DESC LIMIT 20