Question

我的SQL查询有点绊倒了。这是一些背景知识。

架构：

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

我想获得最有序的产品（最大数量）的pid。

我已设法确定最大值：

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

但是我在试图匹配此子查询中的哪些产品时遇到困难。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是一个未知的列。

关于我如何做到这一点或做得更好的任何建议？

Answer 1

您可以JOIN和GROUP BY一样

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，错误q is an unknown column导致q是您尝试在WHERE条件中使用的列别名;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ORDER BY并使用LIMIT 1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

使用带有limit的子查询，您可以采用以下方法：

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 Fiddle Demo

Answer 4

如果您只想要一个最有序的产品，那么卡尔的答案就可以了。如果您想要所有具有相同数量的产品，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
                       );

SQL - 行匹配最大值

4 个答案: