declare	@hour table ( hr int )

declare	@data table ( hr int, value int)

insert into @data(hr, value)
select	1, 10	union all select	2, 20	union all
select	4, 40	union all select	5, 50	union all
select	6, 60

declare	@i int

select @i = 0
while (@i < 24)
begin
	insert into @hour select @i
	select	@i = @i + 1
end

select * from @data

hr          value       
----------- ----------- 
1           10
2           20
4           40
5           50
6           60

(5 row(s) affected)

select 	h.hr, isnull(d.value, 0) as val
from	@hour h left join @data d
on	h.hr	= d.hr

hr          val
----------- ----------- 
0           0
1           10
2           20
3           0
4           40
5           50
6           60
7           0
8           0
9           0
10          0
11          0
12          0
13          0
14          0
15          0
16          0
17          0
18          0
19          0
20          0
21          0
22          0
23          0

(24 row(s) affected)