with rec_user as(
select distinct user_id,
rec_info_l,
hobby_l,
score
from recommend_tb
left join user_action_tb on rec_user=user_id 
where rec_info_l=hobby_l
)

select avg(score) as avg_score from rec_user

虚拟表需要去重，不然总是提示不对。。。。