Question

chat Table
-------------------------------------------------------
msg_id  msg(description of msg)   sender(id)   receiver(id)
-------------------------------------------------------
1       hello                      2             1
1       how are you                1             2
----------------------------------------------------------

user table
-----------------------
u_id   username
-----------------------
1       usman
2       Ali
---------------------

这里你看到两个表用于聊天，一个表用于用户我在这两个表之间建立了关系，但我觉得如何从这些表中提取数据很困难。

我想要的......

我想用其用户名和每个收发器名称及其用户名如Facebook聊天提取每个发件人msg，以便我进行此查询

我把这个查询放在数据库中

select u.user_name UserName,msg.msg
from user u,messages msg 
where (msg.sender or msg.receiver)=(select u_id from user where u_id= 1 )
    and msg.sender=1
order by msg.msg_id desc

但此查询重复发件人邮件，其中包含收件人姓名和发件人姓名

的收件人邮件

我想显示发件人和reciver msg show与他们的名字分开告诉我任何方法我如何解决它。

Answer 1

你拥有的东西永远不会奏效。 or比较将返回一个布尔值true / false值，然后将其与u_id的值进行比较。由于u_id查询被硬编码为仅返回1，因此您有效地执行了where true/false = 1。

您需要加入user表两次（一次为接收者，一次为发件人）：

SELECT sender.user_name, receiver.user_name, msg.msg
FROM msg
LEFT JOIN user AS sender ON msg.sender_id = sender.u_id
LEFT JOIN user AS receiver ON msg.receiver_id = receiver.u_id
ORDER BY msg.msg_id

Answer 2

  select users.name, messages.msg ....          Etc from messages inner join users on       msgs.userid = user.id where                             (sender = :sndr and receiver = :rcvr)         or (sender = :rcvr and receiver= :sndr)  order by date desc;        
                take note of the named parameters there.  That would return the conversation between the two users

如何在mysql中检索发件人和收件人用户名的聊天消息

2 个答案: