您如何查询三个最大的唯一客户Purchase_Cost？
我想应用DISTINCTonly on Customer_Name，但下面的查询将 distinct 应用于所有三列。我应该如何修改查询以获得所需的输出？
SELECT DISTINCT TOP 3 customer_name, order_no, Purchase_Cost
FROM PurchaseTable
ORDER BY Purchase_Cost
AskOverflow.Dev
