上道题同个思路，做好各个表之前的嵌套及条件筛选、最后做好表格的分组及排序即可
select level,
count(*) level_cnt
from exam_record e

join user_info 
using(uid)


join examination_info i
using(exam_id)

where score>80
and tag="SQL"

group by level
order by level_cnt desc