Question

我对基本邮件系统有以下查询。它会显示您发送的消息。但是，它显示sender_id引用的帐户的first_name和second_name。相反，我希望它输出receiver_id

引用的名称列

ie）SELECT first_name，second_name WHERE accounts.account_id = messages.receiver_id

我是否需要为此编写单独的查询，还是可以在单个查询中将其输出？我一直在努力思考这个问题！

SELECT first_name, second_name, message_id, title, body, seen, urgent, type, messages.timestamp 
FROM messages 
INNER JOIN accounts 
ON messages.sender_id=accounts.account_id 
WHERE sender_id = ?

Answer 1

您可以使用两个连接执行此操作：

SELECT s.first_name as sender_first, s.second_name as sender_last,
       r.first_name as rec_first, r.second_name as rec_last,
       m.message_id, m.title, m.body, m.seen, m.urgent, m.type, m.timestamp 
FROM messages m inner join
     accounts s
     ON m.sender_id = s.account_id inner join
     accounts r
     on m.receiver_id = r.account_id
WHERE m.sender_id = ?

引用内部联接查询

1 个答案: