SQL ROW_NUMBER() OVER函數的基本用法用法

語法：ROW_NUMBER() OVER(PARTITION BY COLUMN ORDER BY COLUMN)

例1：SELECT  ROW_NUMBER() OVER(ORDER BY OrderPrice) rownum,OrderPrice FROM [MyTest].[dbo].[Orders]

簡單的說row_number()從1開始，爲每一條分組記錄返回一個數字，這裏的ROW_NUMBER() OVER (ORDER BY OrderPrice DESC) 是先把列OrderPrice降序，再爲降序以後的沒條OrderPrice記錄返回一個序號。 

例2：SELECT  ROW_NUMBER() OVER(PARTITION BY Customer ORDER BY OrderPrice) rownum,OrderPrice,Customer FROM [MyTest].[dbo].[Orders]

row_number() OVER (PARTITION BY Customer ORDER BY OrderPrice) 表示根據Customer 分組，在分組內部根據 OrderPrice排序，而此函數計算的值就表示每組內部排序後的順序編號（組內連續的唯一的)