[SQL] A subselect in an aggregate

[Bryan White]

This statement works:
select date, (select sum(qty * price) from orderdetail d where d.orderid =
orders.orderid) from orders

But when I try to do something like this:

select date, sum(select sum(qty * price) from orderdetail d where d.orderid
= orders.orderid) from orders group by date

I get ERROR: parser: parse error at or near "select"

Is there a way to apply an agregate function to a subselect like this?