row_number() OVER (PARTITION BY COL1 ORDER BY COL2)

select *,ROW_NUMBER() over(partition by deviceID order by RecordDate desc

 

row_number() OVER (PARTITION BY COL1 ORDER BY COL2) 表示根據COL1分組，在分組內部根據 COL2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（組內連續的惟一的)

實例：

初始化數據

create table employee (empid int ,deptid int ,salary decimal(10,2))

insert into employee values(1,10,5500.00)

insert into employee values(2,10,4500.00)

insert into employee values(3,20,1900.00)

insert into employee values(4,20,4800.00)

insert into employee values(5,40,6500.00)

insert into employee values(6,40,14500.00)

insert into employee values(7,40,44500.00)

insert into employee values(8,50,6500.00)

insert into employee values(9,50,7500.00)

數據顯示爲

empid       deptid      salary ----------- ----------- ---------------------------------------

1           10          5500.00

2           10          4500.00

3           20          1900.00

4           20          4800.00

5           40          6500.00

6           40          14500.00

7           40          44500.00

8           50          6500.00

9           50          7500.00

需求：根據部門分組，顯示每一個部門的工資等級

預期結果：

empid       deptid      salary                                  rank ----------- ----------- --------------------------------------- --------------------

1           10          5500.00                                 1

2           10          4500.00                                 2

4           20          4800.00                                 1

3           20          1900.00                                 2

7           40          44500.00                               1

6           40          14500.00                               2

5           40          6500.00                                 3

9           50          7500.00                                 1

8           50          6500.00                                 2

SQL腳本：

SELECT *, Row_Number() OVER (partition by deptid ORDER BY salary desc) rank FROM employee

 

轉自：http://www.cnblogs.com/digjim/archive/2006/09/20/509344.html