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。SELECTmessage.id,message.date_sent,message.object_id,message.content,SubMessage1.content,SubMessage1.id,SubMessage1.date_sent,SubMessage2.content,SubMessage2.id,SubMessage2.date_sentFROMmessagesAsMessageLEFTOUTERJOIN(SELECTmessages.object_idasobject_id,me