Question

I am coding a message system for user communication. In the inbox I do not want to show the user the messages he/she received. I just want to show the conversations. So as an example, if one user send or receive more than one message then in the inbox there should only be the conversation (which includes the newest message, either written or received) with the user and when the user clicks on the conversation he/she can see all past messages.

The table structure (simplified) of ‘messages’ is as followed:

message_id
user_id_sender
user_id_recipient
message

Now the problem is that the messages are saved in a database where each row is one message, so I have to group these messages in a certain way.

The select statement I came up with is the following:

SELECT * FROM messages
WHERE user_id_sender = 1 OR user_id_recipient = 1
GROUP BY user_id_sender

But now I obviously get two messages because one which has been written by user ‘1’ and one that he has received..

Does anybody have an idea how to solve this?

Answer 1

I’ve solved this problem some month ago. I suppose you have also a date field. This query give you a well structured results with date of last message and last message.

$qry = 'SELECT 
CONCAT(GREATEST(user_id_sender,user_id_recipient)," ",LEAST(user_id_sender,user_id_recipient)) AS thread, 
MAX(CONCAT(date,"|",message)) as date_message, 
MAX(date) AS last_message, 
messages.* 
     FROM messages
     WHERE user_id_sender= ? || user_id_recipient=? GROUP BY thread ORDER BY last_message DESC';

$rows = $db->fetchAll($qry, Array($current_user_id,$current_user_id));