题解 | 给出employees表中排名为奇数行的first_name

select B.first_name as first
from 
employees C
INNER join 
(select first_name,rk from
(select first_name, row_number() over(order by first_name) as rk
from employees) as A
where rk % 2 = 1) as B
on B.first_name = C.first_name