Q&A for professional and enthusiast programmers
DECLARE @UserId int = ##UserId## SELECT ( SELECT CAST(COUNT(Id) AS FLOAT) FROM Posts a WHERE a.OwnerUserId = @UserId AND a.PostTypeId = 2 AND (Score = ( SELECT MAX(Score) FROM Posts b WHERE b.ParentId = a.ParentId))) / (SELECT CAST(COUNT(Id) AS FLOAT) FROM Posts c WHERE c.OwnerUserId = @UserId AND c.PostTypeId = 2) * 100 AS TopAnswerRate;