1892. 页面推荐Ⅱ

注意需要删去每个人自己喜欢的pageid

with t1 as (
    select user1_id user_id, user2_id friend from Friendship
    union
    select user2_id, user1_id from Friendship)
SELECT t2.* FROM (
SELECT t1.user_id, page_id, count(distinct friend) friends_likes
from t1 LEFT JOIN Likes L
ON t1.friend = L.user_id 
group by user_id,page_id) t2
LEFT JOIN Likes L1
ON (t2.user_id,t2.page_id) = (L1.user_id,L1.page_id)
WHERE L1.page_id is null