窗口函数2 开窗聚合函数SUM AVG MIN MAX

select * ,sum(salary) over(partition by dname order by hiredate) from employee;
可以用于求公司的开支

 

 

 

select * ,sum(salary) over(partition by dname order by hiredate rows between 3 preceding and current row ) from employee;

 

 从当前行向上开始三行开始相加

select * ,sum(salary) over(partition by dname order by hiredate rows between 3 preceding and 1 following) from employee;
追加后面一行，没有就不加

select * ,sum(salary) over(partition by dname order by hiredate rows between 3 preceding and unbouned following) from employee;
从当前行添加到最后一行

 

 总结：将sum换成avg和min max效果同理