Question

这是我的代码

 $query = $this->db
        ->select('*')        
        ->join('users as receiver', 'receiver.user_id = messages.user1')
        ->join('users as sender', 'sender.user_id = messages.user2')
        ->get('messages')->result_array();

这是数据库

users table 
user_id |username | datetime
  1     | abc1   | 000000000
  2     | abc2   | 000000000

messages table
msg_id | user1 | user2 | msg   | timestamp
  1    | 1     |  2    | hello | 000000000

我想获得两个用户的记录作为发送者和接收者。但这次加入给了我最后一次加入的记录。在这种情况下，我得到发件人的记录。我想要这样的输出

[0] => Array
    (
        [user1] => stdClass Object
            (
                [id] => 1
                [username] => abc1
                [datetime] => 2016-11-07 03:00:00
            )

        [user2] => stdClass Object
            (
                [id] => 2
                [username] => abc2
                [datetime] => 2016-11-07 00:00:00
            )

        [message] => stdClass Object
            (
                [id] => 1
                [message] => hdf
                [timestamp] => 2016-11-06 08:43:26
            )

    )

提前致谢

Answer 1

这是用于创建将为您提供两行

的联合查询的SQL

select * from messages m join users u on u.user_id = m.user1 union all select * from messages m join users u on u.user_id = m.user2;

或一行中两个用户的连接语句

select * from messages m join users u1 on u1.user_id = m.user1 join users u2 on u2.user_id = m.user2;

如何使用join从表中获取两行

1 个答案: