错误答案：

select first_name from 
(select first_name,rank() over(partition by emp_no order by first_name) rank
from employees) t
where t.rank%2=1

正确答案：因为不能对答案进行排序，感觉题目都没有说清楚，对这种题目很无语

select e.first_name 
from employees e 
join
(
    select first_name,rank() over(order by first_name) as rk
    from employees
) t
on e.first_name=t.first_name
where t.rk%2=1