select uid,nick_name,register_time from ( select uid,nick_name,register_time, row_number()over(order by register_time) as rn from user_info ) t where rn <= 3 order by register_time
select uid,nick_name,register_time from ( select uid,nick_name,register_time, row_number()over(order by register_time) as rn from user_info ) t where rn <= 3 order by register_time