Select the Latest Message Between the communication of two user in mysql

Question

I have a simple table maintaining messages between users. The table structure looks like

     sender    receiver   message   sendtime
      1          2              


        

Answer 1

I take 30 mins to find the solution for this problem because I have thew same problem just take it simple

SELECT DISTINCT sent_by FROM messages WHERE sent_to = 1 UNION SELECT DISTINCT sent_to FROM messages WHERE sent_by = 1

Answer 2

To me it feels simpler to use an own ID based on the sender and receiver. No JOIN and just one GROUP BY needed:

SELECT sender, receiver, message, MAX(time)
FROM (
  SELECT *,
    CASE WHEN sender < receiver 
              THEN CONCAT(sender,'&', receiver)
              ELSE CONCAT(receiver,'&', sender) END AS fromto
  FROM data) AS a
GROUP BY fromto

Answer 3

SELECT data.* FROM 
(SELECT MAX(sendtime) AS sendtime 
         FROM data 
         WHERE 1 IN (sender,receiver)
         GROUP BY IF (1 = sender,receiver,sender)) AS latest
LEFT JOIN data ON latest.sendtime = data.sendtime AND 1 IN (data.sender, data.receiver)
GROUP BY IF (1 = data.sender,data.receiver,data.sender)

I recommend to use unique sequence id in your table to avoid external GROUP BY. If you have incrementing unique message_id (i.e. bigger message_id corresponds to later sendtime), the query would be much simpler:

SELECT data.* FROM 
(SELECT MAX(message_id) AS message_id 
         FROM data 
         WHERE 1 IN (sender,receiver)
         GROUP BY IF (1 = sender,receiver,sender)) AS latest
LEFT JOIN data USING(message_id)

Answer 4

Try making message as the primary key and put sender and receiver in 2 separate tables for the same message like this:

Table 1: {message, sender, sendtime}
Table 2: {message, receiver, sendtime}

Answer 5

This will work out

$query = "SELECT * FROM tableName WHERE `sender`='$userNumber' OR `receiver`='$userNumber' ORDER BY `sendtime` DESC LIMIT 0,1";

Answer 6

Try this:

SELECT  Distinct (*)
FROM    tableName   m
WHERE   date =
    (
    SELECT  MAX (date)
    FROM    tableName

    )