SELECT distinct conversation_id FROM ( 
		(SELECT * 
		FROM user_messages_in as m_in 
		WHERE   m_in.receiver_id = $id)
		UNION 
		(SELECT * 
		FROM user_messages_out as m_out 
		WHERE  m_out.sender_id = $id)
		) as t GROUP BY t.conversation_id 
		");

SELECT t.*
 FROM ".$this->db->dbprefix("user_messages_in")." as t
JOIN ( SELECT *  
FROM ".$this->db->dbprefix("user_messages_out")." as m_out
 GROUP BY conversation_id ) g
ON g.conversation_id = t.conversation_id
 WHERE g.sender_id = $id OR t.receiver_id=$id
 GROUP BY conversation_id
ORDER BY id ASC

"SELECT *,CONCAT(first_name,last_name) as full_name FROM (
											SELECT conversation_id,
			message,
			receiver_id,
			sender_id,
			created_on,
			IF(m_in.receiver_id <>$id, 
			   m_in.receiver_id,m_in.sender_id) AS partnerId
	FROM user_messages_in AS m_in
	WHERE m_in.receiver_id = $id 
											UNION 
											SELECT  conversation_id,
			message,
			receiver_id,
			sender_id,
			created_on,
			IF(m_out.sender_id <>$id, 
			  m_out.sender_id,m_out.receiver_id) AS partnerId
											FROM user_messages_out AS m_out
	WHERE m_out.sender_id = $id 
	ORDER BY created_on DESC
	) as m_data
	 INNER JOIN   profiles as user
	ON user.user_id = m_data.partnerId
	 GROUP BY m_data.conversation_id

SELECT * FROM(
	SELECT conversation_id,titel,message,created_on,receiver_id,sender_id,CONCAT(first_name,last_name) AS full_name
	FROM user_messages_in as m_in
	INNER JOIN profiles AS profile
	ON m_in.sender_id = profile.user_id 
	WHERE conversation_id = $con_id AND m_in.receiver_id = $user_id 
						
	UNION
      SELECT conversation_id,titel,message,created_on,receiver_id,sender_id,CONCAT(first_name,last_name) AS full_name
 	FROM user_messages_in AS m_out
	JOIN profiles AS profile 
	ON m_out.sender_id = profile.user_id 
	WHERE conversation_id = $con_id AND m_out.sender_id = $user_id
	)as msg ORDER BY msg.created_on ");