select
    u1.university,
    round(avg(p1.tt),4)
from
    (
        select
            device_id,
            count(question_id) as tt
        from
            question_practice_detail 
        group by
            device_id
    )p1
    left join user_profile u1 on p1.device_id = u1.device_id
group by
    u1.university
order by
    u1.university