请教一下大佬，大框架想的一样，请问我这个出现了什么问题？ select t2.tag, t1.exam_cnt_20, t2.exam_cnt_21, concat(round((t2.exam_cnt_21-t1.exam_cnt_20)/t1.exam_cnt_20*100,1) .'%') growth_rate, t1.exam_cnt_rank_20, t2.exam_cnt_rank_21, (t2.exam_cnt_rank_21-t1.exam_cnt_rank_20) rank_delta from ( select tag,count(submit_time) exam_cnt_20, rank()over(partition by tag order by count(submit_time) desc) exam_cnt_rank_20 from exam_record join examination_info using(exam_id) where year(submit_time)='2020' and month(submit_time)<=6 group by tag )t1 join ( select tag,count(submit_time) exam_cnt_21, rank()over(partition by tag order by count(submit_time) desc) exam_cnt_rank_21 from exam_record join examination_info using(exam_id) where year(submit_time)='2021' and month(submit_time)<=6 group by tag )t2 using(tag) order by growth_rate desc,t2.exam_cnt_21 注意：navicat运行是正确的