sql-server-2008 - group by, order by, 不同的在一起

Question

我有三列（交易者、产品、价格）的表格。我想让每个交易者获得一次，并以最高价格获得该交易者的产品。当我选择以下时，我看到重复的交易者：

select Trader, Product, Max(Price) as Price
from dbo.Sell
group by Trader, Product 
order by Max(Price) desc

上面的查询如何区分交易者？下面的查询不会改变任何东西：

select distinct Trader, Product, Max(Price) as Price
from dbo.Sell
group by Trader, Product 
order by Max(Price) desc

实际上，以下查询几乎是我想要的，但是我想查看产品而不是价格。

select Trader, Max(Price) as Price
from dbo.Sell
group by Trader

Answer 1

试试这个查询，只有当交易者拥有多个具有最高价格的产品时，您才会获得多条记录。

;with cte as (
    select Trader, Max(Price) as Price
    from dbo.Sell
    group by Trader
)
select cte.Trader, s.Product, cte.Price
from cte join dbo.Sell s
         on cte.Trader = s.Trader and cte.Price = s.Price
order by cte.Price desc

第二种方法是使用一个rank()函数，但同样 rank() 函数将为相同的价格记录带来多个记录。

要获得单条记录，您可以使用Row_Number()代替Rank()。

;with cte as (
    select Trader, Product, Price, 
         Rank() over (partition by Trader order by Price desc) rnk
    from dbo.Sell

)
Select Trader, Product, Price 
From cte
Where rnk = 1
Order by Price desc