cannot use alias in ROW_NUMBER() over in SQL Server?

Question

I have to create a row_number column ordered by a grouped sum, when using sql:

select Sales.Name, SUM(Sales.Bill) as billsum, ROW_NUMBER() over (order by billsum DESC) as rn
from Sales group by Sales.Name

It reports error because row_number over cannot parse the "billsum" alias, I have to write:

select Sales.Name, SUM(Sales.Bill) as billsum, ROW_NUMBER() over (order by SUM(Sales.Bill) DESC) as rn
from Sales group by Sales.Name

so here I write SUM(Sales.Bill) twice, is there anyway to use the alias here?

Answer 1

The MSDN docs for the T-SQL OVER clause say:

value_expression cannot refer to expressions or aliases in the select list.