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

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 xlh DESC) 是先把xlh列降序，再为降序以后的没条xlh记录返回一个序号。 示例： xlh           row_num 1700              1 1500              2 1085              3 710                4

row_number() OVER (PARTITION BY COL1 ORDER BY COL2) 表示根据COL1分组，在分组内部根据 COL2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)

实例：

初始化数据

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)

数据显示为

empid       deptid      salary----------- ----------- ---------------------------------------1           10          5500.002           10          4500.003           20          1900.004           20          4800.005           40          6500.006           40          14500.007           40          44500.008           50          6500.009           50          7500.00

需求：根据部门分组，显示每个部门的工资等级

预期结果：

empid       deptid      salary                                  rank----------- ----------- --------------------------------------- --------------------1           10          5500.00                                 12           10          4500.00                                 24           20          4800.00                                 13           20          1900.00                                 27           40          44500.00                                16           40          14500.00                                25           40          6500.00                                 39           50          7500.00                                 18           50          6500.00                                 2

SQL脚本：

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