oracle ROW_NUMBER() OVER (PARTITION BY COL1 ORDER BY COL2)

工作中遇到的一个问题，需要对某列进行分组排序，取其中排序的第一条数据项

用到了row_number() over(partition by col1 order by col2)来解决此问题。

实例准备：

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

insert into employee values(1,10,234.00);
insert into employee values(2,10,1233.00);
insert into employee values(3,20,600.00);
insert into employee values(4,20,4512.00);
insert into employee values(5,30,3424.00);
insert into employee values(6,30,1232.00);
insert into employee values(7,40,4445.00);
insert into employee values(8,40,9999.00);
insert into employee values(9,40,212000.00);

进行查询操作：

select deptid
       ,salary
       ,row_number() over(partition by deptid order by salary desc) as rn
  from employee;

执行结果：

从上面的结果可以看出来是对部门进行分组，按照薪水来进行排序，之后的处理可以根据自己的需求来进行处理就ok了！