select
    first_name as first
from
    employees
where
    emp_no in (
        select
            emp_no
        from
            (
                select
                    emp_no,
                    first_name,
                    row_number() over (
                        order by
                            first_name asc
                    ) as ranking
                from
                    employees
            ) t
        where
            mod(t.ranking, 2) = 1
    )

因为窗口函数出来排序不对 所以重新在原表里查了一下emp_no 虽然麻烦但是应该准确