题解 | 推荐内容准确的用户平均评分

group by 去重
with a as(
select rec_user,rec_info_l
from recommend_tb rt
join user_action_tb uat 
on rt.rec_user = uat.user_id and rt.rec_info_l = uat.hobby_l
group by rec_user,rec_info_l)

select round(avg(u.score),3) as avg_score
from user_action_tb u
where u.user_id in (select rec_user from a) #不能直接in a.rec_user，IN后面需要跟一个值或子查询