SQL Server add all rows where a condition is validate - sql-server

Question

I have a SQL Server database in which I need to add all the cost for a job family.
I have a table like this
Table : work
+-------+-----------+-----------+---------+
| wonum | cost1 | cost2 | wogroup |
+-------+-----------+-----------+---------+
| 1 | 30.12 | 157.14 | 1 |
| 2 | 110.10 | 0.00 | 1 |
| 3 | 12.67 | 45.45 | 1 |
| 4 | 0.00 | 0.00 | 4 |
| 5 | 400.00 | 11.54 | 4 |
+-------+-----------+-----------+---------+
I need to add cost1 and cost2 for all the row who have the same wogroup but only for the on where wonum = wogroup.
Like this
+-------+-----------+-----------+---------+---------+
| wonum | cost1 | cost2 | wogroup | total |
+-------+-----------+-----------+---------+---------+
| 1 | 30.12 | 157.14 | 1 | 355.48 |
| 2 | 110.10 | 0.00 | 1 | null |
| 3 | 12.67 | 45.45 | 1 | null |
| 4 | 0.00 | 0.00 | 4 | 411.54 |
| 5 | 400.00 | 11.54 | 4 | null |
+-------+-----------+-----------+---------+---------+
In a perfect world, the null value would be the sum of cost1 and cost2 for the row but I'm not sure if it is possible...
EDIT: I can only do a select, it is for a BiRT report

Answer 1

Since this can change with more wonum being added, I'd have this as a VIEW
declare #work table (wonum int , cost1 decimal (6,3), cost2 decimal (6,3) , wogroup int)
insert into #work
values
(1,30.12,157.14,1),
(2,110.10,0.00,1),
(3,12.67,45.45,1),
(4,0.00,0.00,4),
(5,400.00,11.54,4)
select
*,
total = case when wonum = min(wonum) over (partition by wogroup) then sum(cost1) over (partition by wogroup) + sum(cost2) over (partition by wogroup) end
from #work
RETURNS
+-------+-----------+-----------+---------+---------+
| wonum | cost1 | cost2 | wogroup | total |
+-------+-----------+-----------+---------+---------+
| 1 | 30.12 | 157.14 | 1 | 355.48 |
| 2 | 110.10 | 0.00 | 1 | null |
| 3 | 12.67 | 45.45 | 1 | null |
| 4 | 0.00 | 0.00 | 4 | 411.54 |
| 5 | 400.00 | 11.54 | 4 | null |
+-------+-----------+-----------+---------+---------+
YOUR QUERY
select
*,
total = case when wonum = min(wonum) over (partition by wogroup)
then sum(cost1) over (partition by wogroup) + sum(cost2) over (partition by wogroup)
else null
end
from work