php - 检查n个用户是否在同一个房间

Question

我有一个 user_to_room 表

roomID | userID 

我使用这个查询来获取房间 ID(取决于 n 个用户 ID)

SELECT   roomID
FROM     user_to_room
WHERE    userID IN (2,5)
GROUP BY roomID
HAVING   COUNT(DISTINCT userID)=2

演示无效:http://www.sqlfiddle.com/#!3/00b4a/1/0

(取自https://stackoverflow.com/a/16511691/1405318)

但此查询还会返回这两个用户所在的房间以及另一个随机用户所在的房间。我需要一个只返回给定用户 (2,3) 所在房间的查询。

一个可行的解决方案是

SELECT DISTINCT roomID
FROM   user_to_room AS x2
WHERE  x2.roomID NOT IN(SELECT DISTINCT roomID 
                     FROM   user_to_room
                     WHERE  roomID IN(SELECT DISTINCT roomID
                                      FROM   user_to_room
                                      WHERE  userID IN ( 5, 2 )
                                      GROUP  BY roomID
                                      HAVING Count(DISTINCT userID) = 2)
                            AND userID NOT IN( 2, 5 ))
AND roomID IN(SELECT DISTINCT roomID
                                      FROM   user_to_room
                                      WHERE  userID IN ( 5, 2 )
                                      GROUP  BY roomID
                                      HAVING Count(DISTINCT userID) = 2)

工作演示:http://www.sqlfiddle.com/#!3/00b4a/2/0

但我认为这太过分了。有什么想法吗？

Answer 1

您应该能够使用与第一个查询相同的查询，但添加一个过滤器以排除用户在 2、5 之外的任何房间:

select roomId
from user_to_room
where userid in (2,5)
  and roomid not in (select roomid
                     from user_to_room
                     where userid not in (2, 5))
group by roomId
having count(distinct userid) = 2;

参见 SQL Fiddle with Demo