with t as (
    select id, name as 'Employee', Salary, DepartmentId, dense_rank() over(partition by DepartmentId  order by salary desc) as 'rank'
    from employee
)

select d.name as 'Department',t.Employee, t.Salary
from t
left join Department as d on t.DepartmentId = d.id
where t.rank <= 3

partition by，按某字段切分,例如partition by 班级，就是每个班级独自排名
order by，与常规order by用法一致，也区分ASC(默认)和DESC，因为排名总得有个依据

如果会用函数的话，这题其实很简单，先算个rank，然后过滤一下rank<=3就行了