Select gender,university, count(device_id) as user_num, avg(active_days_within_30) as avg_active_days, avg(question_cnt) as avg_question_cnt from user_profile group by gender,university count(device_id)这一点没有想到,group by可以单独使用,我一直试图在where后面添加group by,所以一直失败。这道题挺难的