考点：窗口函数-排序函数
易错点：要求结果不排序，所以需要再加一个子查询
select first_name from employees where
first_name in(
select first_name from
(select first_name,row_number()over(order by first_name asc ) as n
from employees) a
where mod(n,2)=1)

一开始我写的结果是按first_name排序的
select first_name from
(select first_name,row_number()over(order by first_name asc ) as n
from employees) a
where mod(n,2)=1