mysql - 限制在子查询内

Question

我有一个消息表，可以包含主要消息和子消息。我想要实现的是只获得前 2 个最近的子消息。

SELECT message.id, message.date_sent,message.object_id, message.content, 
       SubMessage1.content, SubMessage1.id, SubMessage1.date_sent,
       SubMessage2.content, SubMessage2.id, SubMessage2.date_sent
  FROM messages As Message 
  LEFT
 OUTER
  JOIN ( SELECT messages.object_id as object_id, messages.content as content,
                messages.id as id , messages.date_sent as date_sent
           FROM messages
          ORDER
             BY messages.date_sent ASC LIMIT 1,1
       ) as SubMessage1
    ON Message.id = SubMessage1.object_id
  LEFT
 OUTER
  JOIN ( SELECT messages.object_id as object_id, messages.content as content,
                messages.id as id , messages.date_sent as date_sent
           FROM messages
          ORDER
             BY messages.date_sent ASC LIMIT 2,1
       ) as SubMessage2
    ON Message.id = SubMessage2.object_id
 WHERE Message.id = 1

当我取消限制时，我总是得到第一个结果。但是当我输入限制时，我得到空值。有任何想法吗？有什么建议吗？

Answer 1

SELECT * FROM messages WHERE id = 1
Union all
SELECT * FROM messages WHERE object_id=1
ORDER BY date_sent ASC LIMIT 2