Select c.Name, g.Name, Count(u.CityId)
 From User u
  Right outer Join Group g  ON (g.ID = U.GroupID
	And u.Joindate Between @startdate and @enddate)
  Right outer Join City c ON (c.ID = u.CityID)
 Group by c.Name, g.Name
 ORDER BY c.Name, g.Name

select city.name as City, group.name as [Group], 
isnull(subqty.qty, 0) as Qty
from dbo.City
cross join dbo.Group
left outer join 
	(select cityid, groupid, count(*) as Qty
	from dbo.User
	where joindate >= @startdate
	and joindate < @enddate
	group by cityid, groupid) SubQty
	on city.cityid = subqty.cityid
	and group.groupid = subqty.groupid
order by city, group

select cityname as City, groupname as [Groupname], 
isnull(subqty.qty, 0) as Qty
from  (select groupid, group.name groupname, city.name Cityname, cityid 
             from dbo.Group CROSS JOIN city) cartesianX
left outer join 
        (select cityid, groupid, count(*) as Qty
        from dbo.User
        where joindate >= @startdate
        and joindate < @enddate
        group by cityid, groupid) SubQty
        on cartesianX.cityid = subqty.cityid
        and cartesianX.groupid = subqty.groupid
order by cityname, groupname