--populate sample TABLE
create table sal
(date smalldatetime
,client_code char(1)
,salary int)

insert into sal
select '2010/4/1','A',4000 union all
select '2010/4/1','B',6000 union all
select '2010/4/2','B',6000 union all
select '2010/4/4','A',6000 union all
select '2010/4/6','B',8000 union all
select '2010/4/6','A',2000
--(6 row(s) affected)


--POPULATE DATE TABLE --WILL BE NEEDED IN FURTHER STEPS
create table tbl_date
(date smalldatetime)
insert into tbl_date
select '2010/4/1' union all
select '2010/4/2' union all
select '2010/4/3' union all
select '2010/4/4' union all
select '2010/4/5' union all
select '2010/4/6' 
--(6 row(s) affected)



select 
	d1.date
	,x.client_code
	,0 as salary 
 into #temp	
from tbl_date as d1
cross join (select distinct client_code from sal) as x
--(12 row(s) affected)

update t
set t.salary = s.salary
from #temp as t
	join sal as s
		on s.client_code = t.client_code and s.date = t.date
--(6 row(s) affected)		


-- CUMULATIVE RESULTS WITH NULL VALUES ROWS
select 
s1.date
,s1.client_code
,s1.salary
,(select sum(salary) from #temp as s2
		where s2.date <= s1.date
			and s1.client_code = s2.client_code) as sal_cum
from #temp as s1

order by s1.client_code, s1.date