How many language questions are in each difficulty category

questions by category.sql

DECLARE @tagname varchar(20) = ##language:string##

select DifficultyGroup, Count(1) Total,
       avg(cast(ResponseTime as bigint)) as Average,
       stdev(cast(ResponseTime as bigint)) as StandardDev
from 
  (SELECT
         Questions.CreationDate, 
         Questions.Title, 
         Tags.TagName,
         Answers.CreationDate as ResponseDate,
         DateDiff(minute, Questions.CreationDate, Answers.CreationDate) as ResponseTime,
         cast(DATEPART(hour, Questions.CreationDate) as int) as ResponseHour,
         CASE 
              WHEN DateDiff(hour, Questions.CreationDate, Answers.CreationDate) < 5   THEN 'Easy'
              WHEN DateDiff(hour, Questions.CreationDate, Answers.CreationDate) < 24  THEN 'Medium'
              WHEN DateDiff(hour, Questions.CreationDate, Answers.CreationDate) < 144 THEN 'Hard'
              ELSE                                                                         'Hell'
         END as DifficultyGroup
    FROM Posts Questions
    join Posts Answers on Answers.id = Questions.AcceptedAnswerId
    join PostTags ON PostTags.PostId = Questions.Id
    join Tags on Tags.Id = PostTags.TagId
    WHERE Questions.CreationDate > convert(datetime, '01/01/2011', 101)  
                 and TagName = @tagname
) as Responses
group by DifficultyGroup
order by DifficultyGroup