select top 100 tagname
     , sum(cast(p.viewcount as bigint)) as [sum of views]
     , avg(cast(p.viewcount as bigint)) as [average of views]
from posts p
inner join posttags pt on pt.postid = p.id
inner join tags t on t.id = pt.tagid
where p.creationdate > dateadd(m, -1, getdate())
and p.posttypeid = 1
group by tagname
order by 2 desc