题解 | 分组计算练习题

select
    gender,
    university,
    count(gender) as user_num,
    round(avg(active_days_within_30), 1) as avg_active_day,
    round(avg(question_cnt), 1) as avg_question_cnt
from
    user_profile
group by
    gender,university
order by
    gender asc,
    university asc

需要保留小数点后一位，所以必须加上round，count(gender)比count(*)更精准