在表中选择新列

Question

我有表pricedata（参见附件）。我想在此表中添加两个额外的列（MinPrice of Competitor和CompetitorID of MinPrice）。我写了一个代码来获取列MinPrice of Competitor，但我不知道如何获得第二列，任何帮助????

代码：

select a.ValuationDate, a.shop, a.Itemcode, a.OwnPrice,
       a.[sales price competitor], a.[competitor ID], b.MinPrice
from [PriceTable] a
  inner join
      (select ValuationDate, Shop, ItemCode,
              min([sales price competitor]) as MinPrice
       FROM [PriceTable]
       group by ValuationDate, Shop, ItemCode) b
    on  a.ValuationDate = b.ValuationDate
    and a.Shop = b.Shop
    and a.ItemCode = b.ItemCode

实际表格：

必填表：

Answer 1

你走了。希望这会有所帮助。

select 
    a.ValuationDate, 
    a.shop
    a.Itemcode, 
    a.OwnPrice, 
    a.[sales price competitor],
    a.[competitor ID],  
    b.MinPrice ,
    MINCOMPID.[competitor ID] AS 'CompetitorID of MinPrice'
from [PriceTable] a
inner join 
(
select ValuationDate, Shop, ItemCode, min([sales price competitor]) as MinPrice   FROM [PriceTable]
group by ValuationDate, Shop, ItemCode
) b
on a.ValuationDate=b.ValuationDate and a.Shop=b.Shop and a.ItemCode=b.ItemCode
INNER JOIN [PriceTable] AS MINCOMPID
ON MINCOMPID.ValuationDate=b.ValuationDate and MINCOMPID.Shop=b.Shop and MINCOMPID.ItemCode=b.ItemCode AND MINCOMPID.[sales price competitor]=b.MinPrice

Answer 2

看（未经测试）。获取具有最小/最大值的行的常用方法是SELECT TOP（1）.. ORDER BY .. DESC / ASC

select a.ValuationDate, a.shop, a.Itemcode, a.OwnPrice,
       a.[sales price competitor], a.[competitor ID], 
       c.MinPrice, c.[competitor ID]
from [PriceTable] a
cross apply
   (SELECT TOP(1) b.[competitor ID]
              b.[sales price competitor] as MinPrice
    FROM [PriceTable] b     
    WHERE a.ValuationDate = b.ValuationDate
    and a.Shop = b.Shop
    and a.ItemCode = b.ItemCode  
    ORDER BY b.[sales price competitor] DESC) c