Average Time Until Initial Ticket Response, by Month

Select Top 1000000 DatePart(yyyy, htblticket.date) As Year,
  DatePart(mm, htblticket.date) As Month,
  Convert(Decimal(10,4),Avg(Cast(DateDiff(ss, htblticket.date,
  InitialResponseDate.FirstPublicReply) As decimal) / 86400)) As AverageDays
From htblticket
  Inner Join (Select Top 1000000 htblnotes.ticketid,
        Min(htblnotes.date) As FirstPublicReply
      From htblnotes
        Inner Join htblagents On htblagents.userid = htblnotes.userid
      Where htblnotes.notetype = 1
      Group By htblnotes.ticketid) As InitialResponseDate On
    InitialResponseDate.ticketid = htblticket.ticketid
Where htblticket.spam <> 'True'
Group By DatePart(yyyy, htblticket.date),
  DatePart(mm, htblticket.date)
Order By Year Desc,
  Month Desc