Nested expressions
Q: Can I perform nested aggregate query expression such as:
select [Order ID], [Customer ID] from orders
left outer join
(
select [Order ID], sum(Quantity * [Unit Price]) as Total
from [Order Details]
group by [Order ID]
) as details on orders.[Order ID]=details.[Order ID]
A: No, unfortunately as per error value 25516 (SSCE_M_QP_NO_AGG_IN_AGG) in the SQL Server CE Books Online (which you can install locally via the msi located at C:\Program Files\Microsoft SQL Server Compact Edition\v3.1\SDK\Docs when you install the SDK) - "Nested aggregate expressions are not allowed".