获得通过收件人的螺纹消息

我有数据库的模式是这样的：获得通过收件人的螺纹消息

users 
USERNAME (PK), SEX 
Alex, F 
John, M 
Troy, M 
Matt, M 

messages 
ID (PK), CREATOR (FK users), DATE_CREATED 
1, John, 2012-04-15 
2, Troy, 2012-04-16 

message_recipients 
ID, MESSAGE_ID (FK messages), RECIPIENT (FK users), DATE 
1, 1, John, 2012-04-15 
2, 1, Troy, 2012-04-15 
3, 1, Matt, 2012-04-15 
4, 2, Alex, 2012-04-16 
4, 2, John, 2012-04-16

所面临的挑战是这样的，我想有约翰，特洛伊和马特因为只有收件人的邮件ID。

这是我的查询：

SELECT mr1.MESSAGE_ID 
FROM message_recipients mr1, message_recipients mr2 
WHERE mr1.MESSAGE_ID = mr2.MESSAGE_ID 
    AND mr1.RECIPIENT = mr2.RECIPIENT 
    AND mr2.RECIPIENT = 'John' 
    AND mr2.RECIPIENT = 'Troy' 
    AND mr2.RECIPIENT = 'Matt'

上面的SQL显示没有结果。

如果我这样做查询：

SELECT mr1.MESSAGE_ID 
FROM message_recipients mr1, message_recipients mr2 
WHERE mr1.MESSAGE_ID = mr2.MESSAGE_ID 
    AND mr1.RECIPIENT_ID = mr2.RECIPIENT_ID 
    AND (mr2.RECIPIENT_ID = 'John' 
    OR mr2.RECIPIENT_ID = 'Troy' 
    OR mr2.RECIPIENT_ID = 'Matt') 
GROUP BY mr1.MESSAGE_ID

结果：

MESSAGE_ID 
1 
2

上述结果是不正确的，因为我想看到的是只有1（MESSAGE_ID）作为结果。

我做错了什么？有人能启发我吗？

非常感谢你，约翰

来源

2012-04-17 jobun

我真的不知道你想要什么。但是一列不能是3件事。您可以只使用IN语法。就像这样：

SELECT mr1.MESSAGE_ID 
FROM message_recipients mr1, message_recipients mr2 
WHERE mr1.MESSAGE_ID = mr2.MESSAGE_ID 
    AND mr1.RECIPIENT = mr2.RECIPIENT 
    AND mr2.RECIPIENT IN('John','Troy','Matt')

还是OR语法如下：

SELECT mr1.MESSAGE_ID 
    FROM message_recipients mr1, message_recipients mr2 
    WHERE mr1.MESSAGE_ID = mr2.MESSAGE_ID 
     AND mr1.RECIPIENT = mr2.RECIPIENT 
     AND 
     (
     mr2.RECIPIENT = 'John' 
     OR mr2.RECIPIENT = 'Troy' 
     OR mr2.RECIPIENT = 'Matt' 
    )

编辑

我仍然不知道你想要什么。但它听起来有点像你想是这样的：

SELECT 
    m.ID AS MESSAGE_ID, 
    m.CREATOR, 
    mr.RECIPIENT, 
    mr2.RECIPIENT 
FROM 
    messages AS m 
    LEFT JOIN message_recipients AS mr 
     ON m.ID=mr.MESSAGE_ID 
     AND mr.RECIPIENT='Troy' 
    LEFT JOIN message_recipients AS mr2 
     ON m.ID=mr2.MESSAGE_ID 
     AND mr2.RECIPIENT='Matt' 
WHERE 
    m.CREATOR='John'

来源

2012-04-17 06:38:16 Arion

我也试过这个，但它也给出'2'的结果。不是我想要的。 – jobun 2012-04-17 06:42:26

您是否可以更新问题并提供您期望的输出？ – Arion 2012-04-17 06:45:35

我已经更新了我期望的问题和输出。感谢您的回复。 – jobun 2012-04-17 06:59:53

我认为你应该使用OR代替AND

尝试以下：

SELECT mr1.MESSAGE_ID 
FROM message_recipients mr1 LEFT JOIN message_recipients mr2 
ON mr1.MESSAGE_ID = mr2.MESSAGE_ID 
WHERE mr1.RECIPIENT = mr2.RECIPIENT 
    AND (mr2.RECIPIENT = 'John' 
    OR mr2.RECIPIENT = 'Troy' 
    OR mr2.RECIPIENT = 'Matt')

来源

2012-04-17 06:40:27

尝试使用左连接而不是简单连接。尝试查询张贴在这里 – 2012-04-17 06:49:45

给它一个试戴

SELECT mr1.MESSAGE_ID 
FROM message_recipients mr1, message_recipients mr2 
WHERE mr1.MESSAGE_ID = mr2.MESSAGE_ID 
    AND mr1.RECIPIENT = mr2.RECIPIENT 
    AND mr2.RECIPIENT = 'John' 
    AND mr2.RECIPIENT in ('Troy','Matt')

来源

2012-04-17 07:14:47

获得通过收件人的螺纹消息

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