SQL-行是否匹配总和的最大值

Question

我对SQL查询有些了解。 这是一些背景。

架构：

Product(pid, price, color),
Order(cid, pid, quantity),
Customer(cid, name, age)

我想获取订购最多的产品（最大数量）的PID。

我设法用以下方法确定最大值：

Select Max(total) 
From (Select Sum(quantity) as total 
      From Orders Group By pid) as Totals

但是我在尝试匹配该子查询中的产品时陷入困境。 这是我尝试过的：

Select pid, SUM(quantity) as q 
From Orders 
Where q in (
    Select Max(total) 
    From (Select Sum(quantity) as total 
          From Orders 
          Group By pid) as Totals
    ) 
Group By pid

这表示q是未知列。

关于如何做或做得更好的任何建议？

Answer 1

你可以和GROUP BY一起JOIN

select p.*
from product p
join
(select pid from Order
 group by pid having quantity = max(quantity)
) tab on p.pid = tab.pid;

在您发布的查询中，这是错误的q is an unknown column因为q是您要在WHERE条件下尝试使用的列别名； 这是不允许的。

Answer 2

您应该能够在原始查询中简单地包含PID ，因为您正在对其进行分组。 然后按ORDER BY并使用LIMIT 1仅获得最高结果。

SELECT
    pid
   ,Sum(quantity) as total 
FROM
    Orders 
GROUP BY 
    pid
ORDER BY      
    Sum(quantity)
LIMIT 1

Answer 3

这是使用带有limit的子查询来实现的一种方法：

select o.pid, sum(o.quantity)
from `order` o
group by o.pid
having sum(o.quantity) = 
(
    select sum(quantity) 
    from `order`
    group by pid
    order by sum(quantity) desc
    limit 1
)

• SQL小提琴演示

Answer 4

如果您只想要一种订购最多的产品，那么卡尔的答案很好。 如果您希望所有这些都具有相同的数量，那么：

select pid, sum(quantity) as quantity
from orders o
group by pid
having sum(quantity) = (select max(quantity)
                        from (select sum(quantity) as quantity
                              from orders o
                              group by pid
                             ) q
                       );