分析

思路：作为计算字段使用子查询

  • 分组计算销售总数。select sum(quantity) from OrderItems group by prod_id
  • 在Products表中搜索。where OrderItems.prod_id=Products.prod_id

代码

select prod_name,
(select sum(quantity)
from OrderItems
where OrderItems.prod_id=Products.prod_id
group by prod_id
 ) as quant_sold
from Products