[英]SQL query for mutual friends
My MySQL tables structure is like this.我的 MySQL 表结构是这样的。
USER
uid
FRIENDS
fuid,fuid2,fapproved
For each friend relationship I insert 2 records in FRIENDS.对于每个朋友关系,我在 FRIENDS 中插入 2 条记录。 If user 1 is friend of user 2 then the next rows are inserted into FRIENDS
如果用户 1 是用户 2 的朋友,则将下一行插入 FRIENDS
1,2,1
2,1,1
1,3,1
3,1,1
2,3,1
3,2,1
User id 3 is friend of user id 1 and user id 2用户 id 3 是用户 id 1 和用户 id 2 的朋友
How to get user id 3 in one sql query?如何在一个 sql 查询中获取用户 ID 3?
Given two users @friend1 and @friend2 find all the users who are mutual friends of them:给定两个用户@friend1 和@friend2,找出他们共同好友的所有用户:
SELECT user.uid
FROM user
WHERE EXISTS(
SELECT TOP 1 1
FROM Friends
WHERE Friends.fuid = @friend1 AND Friends.fapproved = 1
AND Friends.fuid2 = User.uid
)
AND EXISTS(
SELECT TOP 1 1
FROM Friends
WHERE Friends.fuid = @friend2 AND Friends.fapproved = 1
AND Friends.fuid2 = User.uid
)
$query = "SELECT DISTINCT a.* FROM user a, visitor b, visitor c WHERE b.user_id = c.visitor_id AND b.visitor_id = a.user_id AND c.user_id = a.user_id AND b.user_id=65";
i tried it.我尝试过这个。 it is working.
这是工作。
Try this:尝试这个:
SELECT DISTINCT a.*
FROM user a, friends b, friends c
WHERE b.fuid = c.fuid2
AND b.fuid2 = a.uid
AND c.fuid = a.uid
AND b.fapproved = 1
AND c.fapproved = 1
Test Script(Tried it in MS SQL..):测试脚本(在 MS SQL 中试过):
CREATE TABLE #USER
(
uid INT
)
INSERT #USER VALUES(1)
INSERT #USER VALUES(2)
INSERT #USER VALUES(3)
CREATE TABLE #FRIENDS
(
fuid INT,
fuid2 INT,
fapproved INT
)
INSERT #FRIENDS VALUES(1,2,1)
INSERT #FRIENDS VALUES(2,1,1)
INSERT #FRIENDS VALUES(1,3,1)
INSERT #FRIENDS VALUES(3,1,1)
INSERT #FRIENDS VALUES(2,3,1)
INSERT #FRIENDS VALUES(3,2,1)
SELECT DISTINCT a.*
FROM #user a, #friends b, #friends c
WHERE b.fuid = c.fuid2
AND b.fuid2 = a.uid
AND c.fuid = a.uid
AND b.fapproved = 1
AND c.fapproved = 1
IMO it's more intuitive to find mutual friends with a self-join on the friendships table IMO 在友谊表上找到自我加入的共同朋友更直观
SELECT a.fuid2 FROM facebook_friendships AS b
ON a.fuid = :user_a AND b.fuid = :user_b AND a.fuid2 = b.fuid2
AND a.fapproved = 1 AND b.fapproved = 1
Here are the important conditions in English:以下是英语的重要条件:
So you are basically grabbing all the rows that the conditions I listed above.所以你基本上抓住了我上面列出的条件的所有行。 You may get duplicate results so adding DISTINCT around a.fuid2 would be a good idea.
您可能会得到重复的结果,因此在 a.fuid2 周围添加 DISTINCT 是个好主意。
i'm just starting MySQL and i faced this problem.我刚开始 MySQL 我遇到了这个问题。
personID friendID
6 10
6 2
6 3
8 1
8 2
8 3
/* query for friends */
select f.personID, p.personID, firstName, lastName
from person p
inner join friends f on f.friendID = p.personID
where f.personID = 6;
/* query for common friends */
select f1.personID 'personID 1', f2.personID 'personID 2', f1.friendID 'common friend'
from person p
inner join friends f1 on f1.friendID = p.personID
inner join friends f2 on f2.friendID = p.personID
where f1.personID = 6 and f2.personID = 8 and f1.friendID = f2.friendID;
result:结果:
personID 1 personID 2 common friend
6 8 2
6 8 3
although it's not a direct solution to your problem, you may base the solution here.虽然它不是您问题的直接解决方案,但您可以在此处建立解决方案。
$query = "SELECT f.fuid, f.fuid2 FROM FRIENDS f, USER u WHERE (f.fuid = u.uid or f.fuid2 = u.uid) AND (u.uid = ".$uid.";");
is that what are you searching for?那是你在寻找什么?
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