-- 使用窗口函数select emp_no, birth_date, first_name, last_name, gender, hire_datefrom ( select *, dense_rank() over ( order by hire_Date desc ) rk from employees ) awhere rk = 3 -- 使用自连接select emp_no, birth_date, first_name, last_name, gender, hire_datefrom ( select a.*, count(b.hire_date) as num from e...