Update Table With A Loop Through A Query?

I want to make a SP to update table Product with information I get from table Orderdetail.

Create Procedure UpdateVoorraad
§OrderId (int)
As
Select ProductId, Tal From Orderdetail where OrderId = @OrderId

-- this query get info from table orderdetail : ProductId (integer) and Tal (smallint)

-- Tal = Number of Products

-- Here I want to loop through the query above

-- and for each record in the query I want to update

-- table Product.

Update Product Set Product.Voorraad = Product.Voorraad - Tal where ProductId = ProductId

To do this must I make a create a tempory table, store the query result in the table loop through the table and update table product, or can I try to create a function without a temporary table.