Problem with outer join

Table B:
key_id
1
2

This SQL statement generate the results posted below: This is the result that we want.

select key_id, nvl(sum(value),0)
from A, B
where A.key_id = b.key_Id (+)

Results:

key_id	sum(Value)
1	1000
2	0

The same SQL stmt with the date criteria returns only 1 row.