LeetCode（数据库）- 页面推荐

题目链接：​​点击打开链接​​

题目大意：略。

解题思路：略。

AC 代码

-- 解决方案(1)
WITH t1 AS(SELECT user2_id user_id FROM Friendship WHERE user1_id = 1

UNION

SELECT user1_id FROM Friendship WHERE user2_id = 1)

SELECT DISTINCT page_id recommended_page FROM Likes li JOIN t1 ON li.user_id = t1.user_id
WHERE page_id NOT IN (SELECT page_id FROM Likes WHERE user_id = 1)

-- 解决方案(2)
SELECT DISTINCT page_id AS recommended_page
FROM Likes
WHERE user_id IN (
    SELECT user1_id AS user_id FROM Friendship WHERE user2_id = 1
    UNION ALL
    SELECT user2_id AS user_id FROM Friendship WHERE user1_id = 1
) AND page_id NOT IN (
    SELECT page_id FROM Likes WHERE user_id = 1
)