Funkcja podsumowania — Zastąp NULL

ROLLUP umieszcza null w wierszu sum, więc jeśli chcesz to zastąpić, sugeruję wzięcie istniejącego zapytania i umieszczenie go w podzapytaniu, a następnie użycie CASE na NAME zastąpić null do Total .

Twój kod będzie podobny do tego:

select 
  case when name is null then 'Total' else name end Name,
  sum(Activated) Activated,
  sum(Deactivated) Deactivated
from
(
  select 
    case 
      when (upper(m.email) like '%max.com') then 'MAX'
      when (upper(m.email) like '%tax.com') then 'TAX'
      else 'OTHER'
    end Name, 
  SUM(case when substring(convert(varchar(8),n.created_on,112),1,6) = '201209' then 1 else 0         end) 'Activated',
  SUM(case when substring(convert(varchar(8),m.LastLockoutDate,112),1,6)='201209' then 1 else 0              end) 'Deactivated'
  from membership.user_details d
  inner join membership.aspnet_membership m 
    on m.userid = d.userid
  inner join membership.user_notes n 
    on n.userid = d.userid
    and n.CREATED_ON = (select min(created_on) 
                        from membership.user_notes 
                        where userid = n.userid
                          and note = 'received.')  
  where approved = 1
  group by case when (upper(m.email) like '%max.com') then 'MAX'
        when (upper(m.email) like '%tax.com') then 'TAX'
        else 'OTHER' end     
) src
group by name with rollup

Jeśli nie zapakujesz zapytania w podzapytanie, możesz użyć czegoś takiego:

select
   case when 
     (case 
        when (upper(email) like '%max.com') then 'MAX'
        when (upper(email) like '%tax.com') then 'TAX'
        else 'OTHER'
      end) is null then 'Total'
      else case 
        when (upper(email) like '%max.com') then 'MAX'
        when (upper(email) like '%tax.com') then 'TAX'
        else 'OTHER'
      end end Name,
  SUM(case when substring(convert(varchar(8),n.created_on,112),1,6) = '201209' then 1 else 0 end) 'Activated',
  SUM(case when substring(convert(varchar(8),m.LastLockoutDate,112),1,6)='201209' then 1 else 0 end) 'Deactivated'
from membership.user_details d
inner join membership.aspnet_membership m 
  on m.userid = d.userid
inner join membership.user_notes n 
  on n.userid = d.userid
  and n.CREATED_ON = (select min(created_on) 
                     from membership.user_notes 
                     where userid = n.userid
                       and note = 'received.')  
where approved = 1
group by case when (upper(m.email) like '%max.com') then 'MAX'
        when (upper(m.email) like '%tax.com') then 'TAX'
        else 'OTHER' end with rollup