每年返回前10位

Question

我需要每年返回前10位產品，我如何使用我的以下查詢來執行此操作？

SELECT 
    DP.ProductID 
    , DP.Name 
    , Year(FS.OrderDate) as TheYear 
    , FS.OrderQty 
    , FS.OrderAmount 
FROM dbo.DimProduct AS DP 
LEFT JOIN dbo.FactSales as FS on FS.ProductID = DP.ProductID 

Answer 1

這應該是容易的，如果您的RDBMS支持Window Functions

SELECT ProductID, 
     Name, 
     TheYear, 
     OrderQty, 
     OrderAmount 
FROM  
     (
      SELECT DP.ProductID 
        ,DP.Name 
        ,Year(FS.OrderDate) as TheYear 
        ,FS.OrderQty 
        ,FS.OrderAmount, 
        ,ROW_NUMBER() OVER() (PARTITION BY Year(FS.OrderDate) 
             ORDER BY FS.OrderQty DESC) rn 
      FROM dbo.DimProduct AS DP 
        LEFT JOIN dbo.FactSales as FS 
         on FS.ProductID = DP.ProductID 
     ) s 
WHERE rn <= 10 
ORDER BY TheYear 

• TSQL Ranking Functions

當前查詢會給你10產品基於FS.OrderQty每TheYear既然你有沒有提到了記錄如何排序的標準刪除。

的ROW_NUMBER()（排名函數）將產生數目爲每個組中的序列，在這種情況下Year(FS.OrderDate)，是基於FS.OrderQty整理出來。記錄將根據生成的序列的值過濾掉。

---

但是，如果ROW_NUMBER()不會產生對具有相同FS.OrderQty記錄TIE。如果您想要處理它，請使用DENSE_RANK()而不是ROW_NUMBER()。

Answer 2

您想使用的功能row_number()獲得前10名。這是假設OrderQty定義頂部10：

select t.* 
from (SELECT DP.ProductID, DP.Name, Year(FS.OrderDate) as TheYear, FS.OrderQty, FS.OrderAmount, 
      row_number() over (partition by Year(FS.OrderDate) 
           order by fs.OrderAmount desc 
           ) as seqnum 
     FROM dbo.DimProduct DP LEFT JOIN 
      dbo.FactSales FS 
      on FS.ProductID = DP.ProductID 
    ) t 
where seqnum <= 10; 

功能row_number()列舉行，從1開始，它在每個組內重新開始，根據partition by條款（在你的情況下，該年）定義。數字的排序基於order by子句（在您的案例中，fs.OrderAmount desc）。所以，每年最好的十款產品都會有數字1-10和where條款選擇它們。

Answer 3

SELECT 
    DP.ProductID 
    , DP.Name 
    , Year(FS.OrderDate) as TheYear 
    , FS.OrderQty 
    , FS.OrderAmount 
    , (FS.OrderQty * FS.OrderAmount) AS FS.Total 
FROM dbo.DimProduct AS DP 
LEFT JOIN dbo.FactSales as FS on FS.ProductID = DP.ProductID 
GROUP BY TheYear, DP.ProductID, FS.Total 
ORDER BY FS.Total DESC 
WHERE seqnum <= 10;