use tempdb;
/*
create table A
(
    [date] date not null,
    [num] int
);
insert into A values
('2009-01-01',1),
('2009-01-02',10),
('2009-01-04',12),
('2009-01-08',20),
('2009-01-09',0),
('2009-01-10',1);
*/

declare @startdate datetime,@enddate datetime;
set @startdate='2009-01-01';
set @enddate='2009-01-31';
select B.day_time,ISNULL(A.num,0) as num from
(
select convert(varchar(10),dateadd(day,number,@startdate),120) as day_time
from
    master..spt_values 
where 
    datediff(day,dateadd(day,number,@startdate), @enddate)>=0
    and number>=0 
    and type='p'
) as B
left join A 
ON A.[date] = B.day_time;