题解 | 给出employees表中排名为奇数行的first_name

------- 难崩
select first_name
from employees
where first_name in 
(
select first_name
from (
    select first_name, flag
    from (
        select first_name, rk, if((rk % 2) = 0, 0, 1) as flag
        from 
        (
            select first_name, rank() over(order by first_name) as rk
            from employees
            order by first_name
        ) as t
    ) as t1
    where flag=1
) as t2
)