Question

我无法用英语总结这个问题，所以转换为SQL让我感到困惑。

我有一个用户表和一个关注表

USER
id | first_name | last_name
10 | Homer      | Simpson
12 | Marge      | Simpson
14 | Bart       | Simpson
16 | Lisa       | Simpson

FOLLOW
id | follow_id | follower_id | status
1  | 10        | 12          | APPROVED
2  | 10        | 14          | APPROVED
3  | 16        | 12          | APPROVED
4  | 16        | 14          | APPROVED

基本上，我想向用户推荐他可能想要关注的其他人。

我打算以此为基础：

找到跟随我的所有人，如果我还没有关注他们，建议我按照他们行事
从第一个列表（跟随我），找到他们关注的所有人
对于每一个人，建议我跟随那些人（如果我还没有这样做）

有人能帮助我朝正确的方向发展吗？

在上面的示例数据中

荷马已经被Marge和Bart
反过来，Marge跟随Lisa（Bart也跟随Lisa）

所以，在这个例子中，我想建议荷马遵循：

Marge（因为她跟着他）
巴特（因为他跟着他）
Lisa（因为她被Marge跟随）

在RICHARD的帮助下，这是最终的解决方案（作为一个存储的PROC）

唯一的补充是删除已经被关注的用户。

BEGIN
    SELECT DISTINCT t1.ID,first_name,last_name FROM
    (
        #Users that are following me
        SELECT u.id as ID, u.first_name , u.last_name 
        FROM mchq_user u
        INNER JOIN follow AS f ON u.id = f.follower_id
        WHERE f.follow_id = in_userID
        UNION

        #Users followed by followers of me
        SELECT  f2.follow_id as ID, u2.first_name, u2.last_name
        FROM mchq_user u
        INNER JOIN follow AS f ON u.id = f.follower_id
        INNER JOIN follow AS f2 ON f2.follower_id = u.id
        INNER JOIN mchq_user AS u2 ON u2.id = f2.follow_id
        WHERE f.follow_id = in_userID AND f2.follow_id != in_userID
    ) AS t1
    WHERE t1.Id NOT IN (
        # Users that I follow already
        SELECT u.id
        FROM mchq_user u
        INNER JOIN follow AS f ON u.id = f.follow_id
        WHERE f.follower_id = in_userID
    );
END

Answer 1

您可能需要以下

的子查询

select distinct a.follower_id, b.first_name, b.last_name from follower as a
inner join user as b on b.id =a.follower_id
where follow_id in   (select follower_id 
                             from follow 
                         where follow_id = '10' and status = 'APPROVED');

Answer 2

CREATE TABLE #user (id INT, first_name VARCHAR(50), last_name VARCHAR(50 ))
CREATE TABLE #follow (user_id INT, following_id INT, f_status VARCHAR(50))


INSERT INTO #user ( id, first_name, last_name )
SELECT 10, 'Homer','Simpson' UNION ALL
SELECT 12, 'Marge','Simpson' UNION ALL
SELECT 14, 'Bart','Simpson'  UNION ALL
SELECT 16, 'Lisa','Simpson'

INSERT INTO #follow ( user_id, following_id, f_status )
SELECT  12  ,   10   , 'APPROVED' union all
SELECT  14  ,   10   , 'APPROVED' union all
SELECT  12  ,   16   , 'APPROVED' union all
SELECT  14  ,   16   , 'APPROVED'   

-- Usrs that follow Homer
SELECT id, first_name , last_name 
FROM #user u
INNER JOIN  #follow AS F ON u.id = F.user_id
WHERE f.following_id = 10
UNION
-- Users followed by followers of Homer
SELECT  F2.following_id, u2.first_name, U2.last_name
FROM #user u
INNER JOIN #follow AS F ON u.id = F.user_id 
INNER JOIN #follow AS F2 ON F2.user_id = u.id
INNER JOIN #user AS U2 ON U2.id = F2.following_id
WHERE f.following_id = 10 AND F2.following_id != 10



DROP TABLE #follow
DROP TABLE #user

根据跟随我的人建议我应该遵循的人

2 个答案: