Question

我有2个表，'兴趣'和'users_interests'。

'users_interests'只有userid和interestid个字段。 '兴趣只有id和name。

我只需要找到共享超过3个兴趣ID的用户ID。我被告知涉及自我加入，但我似乎无法让这个工作。

有人说这样的事情可行：

SELECT 
      others.userid 
  FROM interests AS user 
  JOIN interests AS others 
      USING(interestid) 
  WHERE user.userid = 2 
  GROUP BY 
      others.userid 
  ORDER BY COUNT(*) DESC

但我没有运气。

Answer 1

SELECT ui.userid, COUNT(*) AS common_interests
FROM users_interests ui
WHERE ui.interestid IN (
    SELECT ui2.interestid FROM users_interests ui2 WHERE ui2.userid = 2
) 
AND ui.userid <> 2
GROUP BY ui.userid
HAVING common_interests > 3;

请注意userid我们的搜索基于（2）在代码中的两个位置上出现

Answer 2

你说超过3个共同的兴趣ID ，所以你的意思是“至少4”，对吗？

SELECT first1.userid, second1.userid
FROM users_interests first1, users_interests second1,
     users_interests first2, users_interests second2,
     users_interests first3, users_interests second3,
     users_interests first4, users_interests second4
WHERE
    first2.userid=first1.userid AND first3.userid=first1.userid AND first4.userid=first1.userid AND
    second2.userid=second1.userid AND second3.userid=second1.userid AND second4.userid=second1.userid AND
    first1.userid<>second1.userid AND
    first1.interestid=second1.interestid AND
    first2.interestid=second2.interestid AND first2.interestid<>first1.interestid AND
    first3.interestid=second3.interestid AND first3.interestid<>first2.interestid AND first3.interestid<>first1.interestid AND
    first4.interestid=second4.interestid AND first4.interestid<>first3.interestid AND first4.interestid<>first2.interestid AND first4.interestid<>first1.interestid

由于我没有对此进行测试，请记住它可能存在错误，因此只有在您理解的情况下才能使用它。

如果你需要相同的其他共同兴趣，我相信你可以编写代码来动态生成任何数字的查询。此外，如果您需要感兴趣的名称，我相信您将能够将必要的四个联接添加到interests表并将相关列添加到{{1}条款。

如何计算MySQL中的类似兴趣

2 个答案: