select emp_no, birth_date, first_name, last_name, gender, hire_date from ( select emp_no, birth_date, first_name, last_name, gender, hire_date, dense_rank()over(order by hire_date desc) as posn from employees ) as rk where rk.posn = 3 -- 直接用开窗函数，思路非常清晰，先赋予排名再选出...
