#分组计算练习题#

需要重写

SELECT 
gender, university,
COUNT(device_id) AS user_num,
AVG(active_days_within_30) AS avg_active_day,
AVG(question_cnt) AS avg_question_cnt
FROM user_profile
GROUP BY gender, university

遇到的问题：

1. 还不够清楚group by
2. 还不太熟悉在SELECT写多行函数
3. 参考题解写完后，发现忘记写了FROM