那个回答是不对的,rownum不能使用between and,有关rownum的用法可以查询相关网络文件。
select b.id, b.name, b.birthday from
(select a.*,rownum rn from a where rn<=30 order by birthday desc) b
where b.rn>=21;
select * from (
select * from a desc birthday)
where rownum between 21 and 30 ;