由于要求要保留以为小数，所以需要加上ROUNT,提交才算正确，我看了好多都没有添加ROUNT，不知道你们提交时，有没有提示错误。

SELECT
u.university,
ROUND (COUNT(q.question_id) / count(distinct(u.device_id)),1)
as avg_answer_cnt FROM
user_profile AS u JOIN question_practice_detail AS q
on q.device_id = u.device_id group by u.university