题解 | #分组计算练习题#

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;

计数 count 分组 group by 不跟在where后面 多个分组 group by gender， university 逗号隔开。