Question

表用户的表结构，消息如下所示，

Users - ID, Name

Messages - ID, Sender, Receiver, Message

我想连接两个表两次，比如使用users.id加入messages.sender，使用users.id加入messages.receiver。

是否有可能在单个查询中以发件人的ID，发件人姓名，收件人ID，收件人姓名，邮件......（等）获得结果??? ...

Answer 1

是的，您可以根据需要多次加入表格。

SELECT 
  sender.ID AS `sender_id`, 
  sender.Name AS `sender_name`, 
  receiver.ID AS `receiver_id`, 
  receiver.Name AS `receiver_name`, 
  Messages.Message
FROM
  Messages
INNER JOIN
  Users AS sender
ON
  sender.ID = Messages.Sender
INNER JOIN
  Users AS receiver
ON
  receiver.ID = Messages.Receiver

Answer 2

是的，您可以通过命名内部联接来实现：

 select id, s.Name, r.Name from Messages
    inner join users as s on (message.sender = s.id)
    inner join users as r on (merssage.receiver = r.id)

在MySQL中连接两个表两次。可能与否???

2 个答案: