Running total over date range - fill in the missing dates

Question

I have the following table.

DATE  | AMT
10/10 | 300
12/10 | 300
01/11 | 200
03/11 | 100

How do I get the monthly total? A result like -

Answer 1

the main problem is the and have the missing months displayed as well? I don't see how to do it with out an aux table containing the combination of month\year to be displayed:

create table table1(
date datetime,
amt int
)
insert into table1 values ('10/10/2010',100)
insert into table1 values ('12/12/2010',200)
insert into table1 values ('01/01/2011',50)
insert into table1 values ('03/03/2011',500)

truncate table #dates
create table #dates(
_month int,
_year int
)
insert into #dates values(10,2010)
insert into #dates values(11,2010) --missing month
insert into #dates values(12,2010)
insert into #dates values(01,2011)
insert into #dates values(02,2011)--missing month
insert into #dates values(03,2011)


select D._month, D._year, sum(amt)
from #dates D left join TABLE1 T on D._month=month(T.date) and D._year=year(T.date)
group by D._month, D._year