题解 | 推荐内容准确的用户平均评分

select
    avg(score) as avg_score
from 
(
    select 
        user_id,
        hobby_l,
        rec_info_l,
        score
    from recommend_tb a
    left join user_action_tb b
    on a.rec_user=b.user_id
    where 
		---标记
		case 
            when b.hobby_l = a.rec_info_l then 1
            else 0
        end = 1
		---去重
    group by user_id,
        hobby_l,
        rec_info_l,
        score
) t