题解 | 给出employees表中排名为奇数行的first_name

select first_name as first
from (
    select first_name,
    row_number() over () as rn1, -- 原顺序
    row_number() over (order by first_name) as rn2
    from employees
) temp
where mod(rn2, 2)=1
order by rn1