难点：无实际订单的产品soda也返回

根据题目，分析解题思路：

在OrderItems表，根据order_num，计算出已订购的总金额 在Orders表，根据产品id，得出产品名称 用prod_id 列 将Orders表与OrderItems表关联


select
  prod_name,
 count(order_num) as orders
from
  Products a
  left OUTER JOIN OrderItems b on a.prod_id = b.prod_id
 group by prod_name
order by
  prod_name