select i.uid uid,if(m.cnt_m is null,0,m.cnt_m) as act_month_total , if(d.cnt_d is null,0,d.cnt_d) as act_days_2021, if(e.exam_cnt is null,0,e.exam_cnt) as act_days_2021_exam, if(q.question_cnt is null,0,q.question_cnt) as act_days_2021_question from user_info i left join (select uid,count(distinct d...