drop table Ords
select * into Ords from Orders 

create view vwOrds as select OrderDate, count(OrderID) as q, sum(Freight) as s from Ords group by OrderDate

select * from vwOrds

create trigger tr_vwOrds_upd on vwOrds instead of update as 
if not update(s) return
update Ords set Ords.Freight = o.Freight * o.s2 / o.s1 from Ords inner join (select o.OrderID, o.Freight, d.s as s1, i.s as s2 from Ords o inner join deleted d on o.OrderDate = d.OrderDate inner join inserted i on o.OrderDate = i.OrderDate where o.OrderDate = d.OrderDate) o on Ords.OrderID = o.OrderID
 --В одном дне может быть несколько заказов. В этом случае агрегированную сумму по дню разносим в соответствии с пропорциями Freights в этом дне
 
 --o.Freight - Freight данного заказа, идентифицируемого OrderID; o.s1 - старая сумма фрайтов; o.s2 - новая.
 
go

select top  10  * from vwOrds
update vwOrds set s =  10  where OrderDate = '1996-07-04'
update vwOrds set s =  200  where OrderDate = '1996-07-08'
select top  10  * from vwOrds
select top  10  * from Ords