给出employees表中排名为奇数行的first_name

# 先将数据原来顺序进行排名，以及按照first_name升序进行排名得到
with t1 as (
    select first_name, ROW_NUMBER() OVER() as t_rank1, ROW_NUMBER() OVER (ORDER BY first_name) as t_rank2
    from employees
)
# 想要排名为奇数
select first_name as first
from t1
where MOD(t_rank2, 2) != 0
order by t_rank1;