员工薪资中位数（569）

    Create table If Not Exists Employee (Id int, Company varchar(255), Salary int)
    Truncate table Employee
    insert into Employee (Id, Company, Salary) values ('1', 'A', '2341')
    insert into Employee (Id, Company, Salary) values ('2', 'A', '341')
    insert into Employee (Id, Company, Salary) values ('3', 'A', '15')
    insert into Employee (Id, Company, Salary) values ('4', 'A', '15314')
    insert into Employee (Id, Company, Salary) values ('5', 'A', '451')
    insert into Employee (Id, Company, Salary) values ('6', 'A', '513')
    insert into Employee (Id, Company, Sa