mysql - SQL Join 给出 30 个相同的结果

Question

我正在使用联接从两个表获取消息

表消息: ID、发送者、接收者、消息、密码

表自己的消息: ID、发送者、接收者、消息、密码

查询:

SELECT DISTINCT(Messages.ID) as F_id, 
               Messages.Message as F_message, 
               Messages.Password as F_password, 
               Messages.Receiver as F_receiver, 
               OwnMessages.ID as O_id, 
               OwnMessages.Message as O_message, 
               OwnMessages.Password as O_password, 
               OwnMessages.Sender as O_sender
FROM Messages
JOIN OwnMessages on Messages.Receiver = OwnMessages.Sender
WHERE Messages.Receiver = 8 AND OwnMessages.Sender = 8

Messages 表中的所有内容都显示正确，但 OwnMessages 表中我得到第一行 30 次。有什么想法吗？

Answer 1

SELECT DISTINCT 
               Messages.ID as F_id, 
               Messages.Message as F_message, 
               Messages.Password as F_password, 
               Messages.Receiver as F_receiver, 
               OwnMessages.ID as O_id, 
               OwnMessages.Message as O_message, 
               OwnMessages.Password as O_password, 
               OwnMessages.Sender as O_sender
FROM Messages
INNER JOIN OwnMessages on Messages.Receiver = OwnMessages.Sender
WHERE Messages.Receiver = 8 AND OwnMessages.Sender = 8

或

SELECT             Messages.ID as F_id, 
                   Messages.Message as F_message, 
                   Messages.Password as F_password, 
                   Messages.Receiver as F_receiver, 
                   OwnMessages.ID as O_id, 
                   OwnMessages.Message as O_message, 
                   OwnMessages.Password as O_password, 
                   OwnMessages.Sender as O_sender
    FROM Messages
    INNER JOIN OwnMessages on Messages.Receiver = OwnMessages.Sender
    WHERE Messages.Receiver = 8 AND OwnMessages.Sender = 8
    GROUP BY Messages.ID
    HAVING COUNT(*) = 1