Question

I have two mysql tables Users & Messages. Please will you help me to create an sql query which returns only the most recent message either sent or received by the logged in user Mike ( user_id=1 ) along with the message_id, message_text & first_name of the person who the message was sent to or received from. Ordered by message_id in descending order.

So far i have the query:-

SELECT message_id, first_name, message_text FROM tbl_users, tbl_messages 
WHERE 
(tbl_users.user_id = tbl_messages.sender_id AND tbl_messages.receiver_id = 1 
OR tbl_users.user_id = tbl_messages.receiver_id AND tbl_messages.sender_id = 1) 
GROUP BY tbl_users.first_name
ORDER BY message_id DESC

Which gives the result in the image below. It seems the ORDER BY is being ignored

Thank you in advance

tbl_users

---------------------------
| user_id |  first_name   |
---------------------------
| 1       |  Mike         |
| 2       |  John         |
| 3       |  George       |
| 4       |  Peter        |
| 5       |  Sarah        |
---------------------------

tbl_messages

----------------------------------------------------------------
| message_id |  sender_id   |  receiver_id   |  message_text   |
----------------------------------------------------------------
| 1          |  2           | 1              |  Hello          |
| 2          |  3           | 1              |  How are you    |
| 3          |  1           | 5              |  Hi there       |
| 4          |  2           | 1              |  Greetings      |
| 5          |  1           | 4              |  Good day       |
| 6          |  3           | 1              |  Hi             |
| 7          |  5           | 1              |  A message      |
| 8          |  5           | 4              |  Good morning   |
| 9          |  1           | 5              |  Hello dear     |
| 10         |  1           | 3              |  Howdy          |
----------------------------------------------------------------

Desired result

----------------------------------------------
| message_id |  first_name  |  message_text  |
----------------------------------------------
| 10         |  George      | Howdy          |
| 9          |  Sarah       | Hello dear     |
| 5          |  Peter       | Good day       |
| 4          |  John        | Greetings      |
----------------------------------------------

Database is available here

Answer 1

Just adding a GROUP BY clause may solve your problem, try this…

SELECT message_id, first_name, message_text FROM tbl_users, tbl_messages 
WHERE  
(tbl_users.user_id = tbl_messages.sender_id AND tbl_messages.receiver_id = 1 
OR tbl_users.user_id = tbl_messages.receiver_id AND tbl_messages.sender_id = 1) 
GROUP BY tbl_users.user_id
ORDER BY message_id DESC

UPDATE: Changing the whole query

SELECT t2.message_id, t2.first_name, t2.message_text FROM
(SELECT u.user_id, m.message_id, u.first_name, m.message_text FROM `tbl_users` u
  JOIN `tbl_messages` m ON (u.user_id = m.sender_id AND m.receiver_id = 1)
    OR (u.user_id = m.receiver_id AND m.sender_id = 1) 
  ORDER BY m.message_id DESC
) t2
GROUP BY t2.user_id
ORDER BY t2.message_id DESC

RESULT:

+------------+------------+--------------+
| message_id | first_name | message_text |
+------------+------------+--------------+
| 10         | George     | Howdy        |
| 9          | Sarah      | Hello dear   |
| 5          | Peter      | Good Day     |
| 4          | John       | Greetings    |