SQL ROW_NUMBER() OVER函数的基本用法用法

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

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

简单的说row_number()从1开始，为每一条分组记录返回一个数字，这里的ROW_NUMBER() OVER (ORDER BY OrderPrice DESC)
是先把列OrderPrice降序，再为降序以后的没条OrderPrice记录返回一个序号。 

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) 表示根据Customer 分组，在分组内部根据 OrderPrice排序，而此函数计算的值就表示每组内部排序后的顺序编号（组内连续的唯一的)