使用PHP / MYSQL进行基于会话的消息传递？

Okay so I'm trying to make it so I can make a conversation based messaging system with one table. The user messages a user and we put their id as sent_id and the person who sent it is my_id. Now my problem is, it is displaying, but I don't want it to display more than once. I've been using DISTINCT but that doesn't seem to be working. Example table:

|--ID--|--MY_ID--|--SENT_ID--|
   1        1          2
   2        2          1
   3        1          2

How do I make it only display the latest one?

(Also $my_id is already escaped, don't worry lol)

SELECT `my_id`, `sent_id`, `time_stamp` FROM `messages` WHERE `sent_id`="'.$my_id.'" || `my_id`="'.$my_id.'"

Here is my table:

CREATE TABLE IF NOT EXISTS `messages` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `my_id` text NOT NULL,
  `sent_id` text NOT NULL,
  `message` text NOT NULL,
  `file` text NOT NULL,
  `time_stamp` text NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=MyISAM  DEFAULT CHARSET=utf8 AUTO_INCREMENT=3 ;

Jake, not a 100% sure what you mean about the latest one. Are you talking about ORDER BY DESC?

SELECT `my_id`, `sent_id`, `time_stamp` 
FROM `messages` 
WHERE `sent_id`="'.$my_id.'" || `my_id`="'.$my_id.'"
ORDER BY id DESC
LIMIT 1