set nocount on
declare @a table(starttime  datetime,endtime  datetime,qty  int) 
insert into @a select '2008/08/12','2010/03/06',790 

select t.*,year(t.starttime1) [year],
  days=datediff(day,t.starttime1,t.endtime1),
  qty1=ceiling(datediff(day,t.starttime1,t.endtime1)*(select cast(qty as dec(18,4))/datediff(day,starttime,endtime) from @a))
from (
      select 
        starttime1=case when year(dateadd(yy,b.id-1,a.starttime)) = year(a.starttime) then a.starttime
                        else ltrim(year(dateadd(yy,b.id-1,a.starttime)))+'/01/01'
                        end,
        endtime1=case when year(a.endtime) > year(dateadd(yy,b.id-1,a.starttime)) then ltrim(year(dateadd(yy,b.id-1,a.starttime)))+'/12/31'
                        else a.endtime
                        end
      from @a a,
          (select id 
           from sysobjects 
           where id<=(select datediff(yy,starttime,endtime)+1 
                      from @a)
           ) as b
     ) t

-->结果(有点尾差)

starttime1                      endtime1        year    days    qty1 
-----------------------  ---------------------- ----    ----    ----
2008-08-12 00:00:00.000    2008-12-31 00:00:00.000    2008    141    196
2009-01-01 00:00:00.000    2009-12-31 00:00:00.000    2009    364    504
2010-01-01 00:00:00.000    2010-03-06 00:00:00.000    2010    64    89