Messaging System with PHP/MySQL

Question

Hi I'm trying to make a messaging system with php and mysql.

The mysql table is simple: id sender receiver text timestamp

I'm trying to make the messaging somewhat like Facebook/Twitter so the list is in 'conversations' and the last message in the conversation is viewed.

This is what I have atm:

(SELECT * FROM messages WHERE receiver = 13 OR sender = 13 GROUP BY receiver,sender ORDER BY id ASC) ORDER BY id ASC

Answer 1

SELECT messages.* FROM messages, (SELECT MAX(id) as lastid FROM messages 
WHERE receiver = 13 OR sender = 13 
GROUP BY CONCAT(LEAST(receiver,sender),'.',GREATEST(receiver,sender))) as conversations
WHERE id = conversations.lastid
ORDER BY timestamp DESC

what you need is a unique conversation id between the chat-partners. i've simulated this with the subquery, hope this helps

Answer 2

Use DESC for fetch new rows, default is ASC

   (SELECT * FROM messages WHERE receiver = 13 OR sender = 13 GROUP BY receiver,sender ORDER BY id DESC)

AND SET LIMIT 1 ,1 AFTER ORDER BY

I think you need to

(receiver = '{receiver id}' AND sender = '{sender id}' ) OR (receiver ='{sender id}' AND sender = '{receiver id}' )

Answer 3

UPDAte: I'm not sure if it works perfect:

SELECT * FROM messages 
WHERE receiver = 13
GROUP BY receiver,sender 
ORDER BY timestamp DESC
LIMIT 1

UNION ALL
SELECT * FROM messages 
WHERE sender = 13
GROUP BY receiver,sender 
ORDER BY timestamp DESC
LIMIT 1

to reverse the order:

ORDER BY timestamp DESC