獲取SQL Server中每個組中的頂級ID

Question

我想添加一個包含每個組中第一個的列。

樣品：

Product  ID 
Orange  1 
Orange  2 
Orange  3 
Orange  4 
Apple   5 
Apple   6 
Apple   7 
Grapes  8 
Grapes  9 

所需的輸出：

Product  ID 
Orange  1 
Orange  1 
Orange  1 
Orange  1 
Apple   5 
Apple   5 
Apple   5 
Grapes  8 
Grapes  8 

Answer 1

您可以使用MIN(ID) OVER (PARTITION BY Product)：

SELECT Product, 
     ID = MIN(ID) OVER (PARTITION BY Product) 
FROM dbo.Products 
ORDER BY ID 

Demo

今天文章：Understanding the OVER clause

Answer 2

我覺得Tim是正確的！ 其他情況下，您可以使用： SELECT P.Product FROM dbo.Products P CROSS APPLY (SELECT TOP 1 ID FROM dbo.Products WHERE Product = P.Product ORDER BY ID)