我怎样才能将减法计数分组

我有一个订单详细信息表，其中包含订单详细信息，我需要计算每个产品的销售额减去每个产品的退款（退回）订单。

ex: total sales of product = sales orders total - returned orders of a product

注意：我使用了交易类型字段，这样我就可以过滤订单类型。

订单详细信息表字段。

ID - Productname - Price - ono - transaction_type
11 - prod1       - 100.00- 1   - salesorder
12 - prod2       - 200.00- 2   - salesorder
13 - prod1       - 100.00- 1   - returned
14 - prod2       - 200.00- 3   - salesorder
15 - prod2       - 200.00- 4   - salesorder

我对的要求

Productname - Total sales
Prod1       - 0
Prod2       - 3

Select Product_NAME, Sum(Case when transaction_type='salesorder' then 1 Else 0 End)- Sum(Case when transaction_type!='salesorder' then 1 Else 0 End) as TotalSale
from OrderDetals group by Product_NAME

SELECT ProductName, 
SUM(CASE WHEN [transaction_type] = 'salesorder' THEN [Quentity] ELSE -1 * [Quentity] END) AS [Total Number Of Sale]
FROM your_table)name
GROUP BY ProductName