select sum(votes) as votes, orderbyYear, orderbyMonth from (
select
case
when votetypeid = 2 then 1
when votetypeid = 3 then -1
end as votes,
datepart(mm, creationdate) as orderbyMonth,
datepart(yyyy, creationdate) as orderbyYear
from votes where votetypeid in (2,3)
) votes group by orderbyYear, orderbyMonth order by orderbyYear, orderbyMonth