复杂的SQL查询

Question

我的数据库看起来是这样的：

• Customer (c_id, c_name)
• Products (p_id, p_name, p_cost)
• Buys (p_id references Products, c_id references Customer)

我想查询以下数据库：

• 客户w^ith最大产品数量：如果有2个或更多客户有相同数量的产品，那么将考虑所有产品的总价格

我试过了，但它显示错误消息：“语法不正确附近）“。

我想调试它没有收获。

任何人都可以调试此查询，甚至建议一个更优化的查询？

select a1.c_id, a1.c_name 
from 
    (select c.c_id, c.c_name 
    from Customer c 
    where c.c_id in 
     (select b.c_id 
      from Buys b 
      group by b.c_id 
      having COUNT(b.p_id) >= all 
      (
       select COUNT(b.p_id) 
       from Buys b 
       group by b.c_id 
     ) 
    ) 
) 
as a1 
join 
    (select b.c_id, SUM(p.p_cost) as 'SumCost' 
    from Buys b 
    join Products p on b.p_id = p.p_id 
    group by b.c_id 
    ) as a2 on a1.c_id = a2.c_id 
where 
    a2.SumCost = (select MAX(SumCost) 
        from 
         (select b.c_id, SUM(p.p_cost) as 'SumCost' 
         from Buys b 
         join Products p on b.p_id = p.p_id 
         group by b.c_id 
        ) 
       ) 

更新：

上面的查询是由mohdowais成功调试。 我现在认为这个查询效率不高。你们都可以请建议一个更有效的吗？ 我没有使用任何索引。

Answer 1

您需要添加一个派生表说明符的最后一个选择：

select a1.c_id,a1.c_name 
    from 
    (
    select c.c_id,c.c_name 
    from Customer c 
    where c.c_id in 
    (
     select b.c_id 
     from Buys b 
     group by b.c_id 
     having COUNT(b.p_id)>=all 
     (
      select COUNT(b.p_id) 
      from Buys b 
      group by b.c_id 
     ) 
    ) 
) 
as a1 join (
        select b.c_id,SUM(p.p_cost) as 'SumCost' 
        from Buys b join Products p on (b.p_id=p.p_id) 
        group by b.c_id 
       ) 
       as a2 on (a1.c_id=a2.c_id) 

       where a2.SumCost= 
       (
        select MAX(SumCost) 
        from 
        (
         select b.c_id,SUM(p.p_cost) as 'SumCost' 
         from Buys b join Products p on (b.p_id=p.p_id) 
         group by b.c_id 
        ) maxTmp -- <----------------- 
       ) 

[我不能为你查询的正确性和效率虽然发表评论，如果没有表架构，索引和实例数据]