汇总查询在列上有连接和计算？

Question

我有我的汇总查询

  Select   
      CASE 
         WHEN (GROUPING(p. product_name ) = 1) THEN 'Total'
         ELSE p. product_name END AS ProductName,
  (( o.item_price - o.discount_amount )*  o.quantity) as Total_Amount  

  from 
      products as p
  inner join 
      order_items as o on o.product_id  = p.product_id
  group by  
      p.product_name, (( o.item_price - o.discount_amount )* o.quantity) with rollup

它返回最后一行 NULL 值不给出总数 请解决这个为什么我得到总数为空

实际上，我正在使用连接和计算（如 itemprice 减去折扣并乘以数量）来获取记录，现在将 ROLLUP 应用于计算字段

Answer 1

select中需要一个聚合函数：

Select (CASE WHEN (GROUPING(p. product_name ) = 1) THEN 'Total'
             ELSE p.product_name
        END) AS ProductName,
      sum((o.item_price - o.discount_amount )*o.quantity) as Total_Amount  
from products p inner join 
     order_items o
     on o.product_id  = p.product_id
group by p.product_name with rollup;