获取SQL Server中每个组中的顶级ID

Question

我想添加一个包含每个组中第一个的列。

样品：

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

所需的输出：

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

我觉得Tim是正确的！ 其他情况下，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)