2

我有 2 个表，我想从中获取用户数据。

表格1 ： frei_session

username    session_id

Prince      51
Dilip       49
Sumit       50

表 2： friendrequest

requestTo   requestFrom     status

49              50              C
50              51              C
49              51              P

朋友请求表显示用户之间的关系，其中C代表Complete，P代表Pending。表示如果status = C两者都是朋友并且status = P请求是否待处理。

frei_session表显示网站的所有在线用户。

我只想限制与朋友的聊天。我尝试了以下查询，但它显示了所有在线用户

假设用户49在线

SELECT DISTINCT f.username,f.session_id
    FROM frei_session AS f
    LEFT JOIN friendrequest AS fr ON fr.requestFrom=f.session_id
    LEFT JOIN friendrequest AS frnd ON frnd.requestTo=f.session_id
    WHERE (fr.requestFrom<>49 OR frnd.requestTo<>49) AND (fr.status = 'C' OR frnd.status = 'C')

此查询向我显示这样的输出

username    session_id

Prince          51
Sumit           50

但我想要这样的输出

username    session_id

Sumit       50

因为用户51和用户49不是朋友

4

5 回答 5

4 
SELECT  IF(a.RequestTo = 49, c.userName, b.userName) username,
        IF(a.RequestTo = 49, c.session_ID, b.session_ID) Session_ID
FROM    friendRequest a
        INNER JOIN frei_session b
            ON a.requestTo = b.session_ID
        INNER JOIN frei_session c
            ON a.requestFrom = c.session_ID
WHERE   a.status = 'C' AND
        49 IN (a.requestTo, a.requestFrom)

结果

╔══════════╦════════════╗
║ USERNAME ║ SESSION_ID ║
╠══════════╬════════════╣
║ Sumit    ║         50 ║
╚══════════╩════════════╝

更新 1

DELIMITER $$
CREATE PROCEDURE ShowAllUserName(IN _sessionID INT)
BEGIN
    SELECT  IF(a.RequestTo = _sessionID, c.userName, b.userName) username,
            IF(a.RequestTo = _sessionID, c.session_ID, b.session_ID) Session_ID
    FROM    friendRequest a
            INNER JOIN frei_session b
                ON a.requestTo = b.session_ID
            INNER JOIN frei_session c
                ON a.requestFrom = c.session_ID
    WHERE   a.status = 'C' AND
            _sessionID IN (a.requestTo, a.requestFrom);
END;
DELIMITER $$

调用过程时，

CALL ShowAllUserName(49);
于 2013-03-09T10:13:18.340 回答
2

你为什么要加入同一张桌子两次？

尝试

LEFT JOIN friendrequest AS fr ON fr.requestFrom=f.session_id AND fr.requestTo=f.session_id

比，您可以通过以下方式更改您的 where 查询：

WHERE fr.requestFrom<>49 AND fr.status = 'C'

GROUP BY fr.status如果我确实了解您的问题，我会尝试，它可能会起作用。

于 2013-03-09T10:02:36.110 回答
2

尝试使用此查询：

SELECT DISTINCT f.username,f.session_id
FROM frei_session AS f
LEFT JOIN friendrequest AS fr ON f.session_id IN (fr.requestFrom, fr.requestTo)
WHERE fr.requestFrom = 49 AND fr.status = 'C'
于 2013-03-09T10:08:33.593 回答
0

您可以先获取收到 Dilip 请求的用户。然后，您将获取已向 Dilip 发送请求的用户。之后，您联合这些用户。SQL 类似于：

SELECT fs.username, fs.session_id
FROM   frei_session AS fs, friendrequest AS fr
WHERE  fs.username = "Dilip"
  AND  fs.session_id = fr.requestFrom
  AND  fr.status = "C"
UNION
SELECT fs.username, fs.session_id
FROM   frei_session AS fs, friendrequest AS fr
WHERE  fs.username = "Dilip"
  AND  fs.session_id = fr.requestTo
  AND  fr.status = "C"

我相信这个解决方案更容易理解。

于 2013-03-09T15:08:33.830 回答
0 
SELECT  IF(a.RequestTo = 49, c.userName, b.userName) username,
        IF(a.RequestTo = 49, c.session_ID, b.session_ID) Session_ID
FROM    friendRequest a
        INNER JOIN frei_session b
            ON a.requestTo = b.session_ID
        INNER JOIN frei_session c

            ON a.requestFrom = c.session_ID
WHERE   a.status = 'C' AND
        49 IN (a.requestTo, a.requestFrom)
于 2013-03-29T12:31:19.100 回答