Question

想请你帮忙

让我Sql query列出所有订单，但我需要添加OrderStatus OrderStatusID

SELECT DISTINCT 
    a.OrderNr, 
    a.CompanyName, 
    max(a.OrderStatusID) AS 'xxx'

FROM [NB].[dbo].[Npos] as a
INNER JOIN [NB].[dbo].[Npos_Order_Status_Name] as b 
ON 
a.OrderStatusID = b.OrderStatusID

GROUP BY  OrderNr, CompanyName

[NB].[dbo].[Npos_Order_Status_Name]中的

是

OrderStatusID | OrderStatusName
--------------------------------
            0 | Start
            1 | Stop
            2 | Pause

我用inner join尝试过，但我做错了。

谢谢

Answer 1

我相信这个查询会做你想做的事情

SELECT t.OrderNr, t.CompanyName, b.OrderStatusName
FROM
(
   SELECT 
    OrderNr, 
    CompanyName, 
    max(OrderStatusID) AS 'maxOrderStatus'
  FROM [NB].[dbo].[Npos]
  GROUP BY  OrderNr, CompanyName
) t
JOIN [NB].[dbo].[Npos_Order_Status_Name] as b 
  ON  t.maxOrderStatus = b.OrderStatusID

或使用窗口函数

SELECT t.*
FROM
(     
    SELECT
        a.*,
        row_number() over (partition by OrderNr, CompanyName order by OrderStatusID desc) rn
    FROM [NB].[dbo].[Npos] as a
    INNER JOIN [NB].[dbo].[Npos_Order_Status_Name] as b 
      ON a.OrderStatusID = b.OrderStatusID
) t
WHERE rn = 1

但是，根据我的经验，在某些情况下，第二种变体可能稍慢。

带有JOIN的SQL max（）

1 个答案: