select tag, sum(case when start_year = 2020 then exam_cnt else 0 end) as exam_cnt_20, sum(case when start_year = 2021 then exam_cnt else 0 end) as exam_cnt_21, concat(round(((sum(case when start_year = 2021 then exam_cnt else 0 end)-sum(case when start_year = 2020 then exam_cnt else 0 end))/sum(case...
