Question

我需要帮助构建一个SQL查询，该查询返回订单中前2项的展平结果。

表格和相关字段如下：

Order        OrderItem       
-------      -----------     
orderId      orderId         
             productCode     
             quantity

我正在寻找所需的结果集：

[orderId]    [productCode1]    [quantity1]    [productCode2]    [quantity2]
----------   --------------    -----------    --------------    -----------
o123         p134              3              p947              1   
o456         p384              2              p576              1

结果将按orderId的{{1}}分组，Order的{{1}}来自productCode。我不在乎哪个TOP 2会被退回，只需要两个。

非常感谢任何帮助。

Answer 1

您可以使用条件聚合和窗口函数row_number()执行此操作：

select orderId,
       max(case when seqnum = 1 then ProductCode end) as ProductCode1,
       max(case when seqnum = 1 then Quantity end) as Quantity1,
       max(case when seqnum = 2 then ProductCode end) as ProductCode2,
       max(case when seqnum = 2 then Quantity end) as Quantity2
from (select oi.*,
             row_number() over (partition by orderId order by quantity desc) as seqnum
      from OrderItem oi
     ) oi
group by orderId;

Answer 2

假设您正在使用SQL Server 2005或更高版本，您可以创建由ProductCode排序的CTE，然后在第二个CTE中将排名为2且最后join的行带到{{1 }}

Orders

Answer 3

select
    o.orderId,
    max(case when row_num = 1 then oi.ProductCode end) as ProductCode1,
    max(case when row_num = 1 then oi.Quantity end) as Quantity1,
    max(case when row_num = 2 then oi.ProductCode end) as ProductCode2,
    max(case when row_num = 2 then oi.Quantity end) as Quantity2
from Order as o
   outer apply (
       select top 2
           oi.*, row_number() over (order by oi.productCode) as row_num
       from OrderItem as oi
       where oi.orderId = o.orderId
   ) as oi
group by o.orderId

SQL查询展平订单和最高订单项

3 个答案: