SQL中有多个但单独的WHERE条件？

Question

I'm trying to get user messages from the database where the user is either the sender or the recipient with one other unique user, and I can't figure out how to write the WHERE statement. This is what I have now:

$sql = " SELECT sender, 
       receiver, 
       timestamp, 
       message 
FROM   messages 
WHERE  ( receiver = '$log_username' 
         AND sender = '$messageOther' ) 
        OR ( receiver = '$messageOther' 
             AND sender = '$log_username' ) 
ORDER  BY timestamp DESC";
$query = mysqli_query($db_conx, $sql);
while($row = mysqli_fetch_array($query, MYSQLI_ASSOC)) {
    $message = $row["message"];
    $sender = $row["sender"];
    $receiver = $row["receiver"];
    $timestamp = $row["timestamp"];
    $messagehtml .= 'Sender: '.$sender.' | Receiver: '.$receiver.' | Message: '.$message.' | Timestamp '.$timestamp.'<br />';
    }

What's the best way of writing this to get that result?

Answer 1

If you mean that $log_username should be either sender or receiver and the other value $messageOther should be either sender or receiver following query will work for you:

SELECT sender, receiver, timestamp, message 
FROM messages 
WHERE ((receiver='$log_username' AND sender='$messageOther') OR
(receiver='$messageOther' AND sender='$log_username'))
ORDER BY timestamp DESC

sqlfiddle

Well instead of AND you need to use OR everywhere. Try following, it works on my test table:

 
 
 
  
  SELECT sender, receiver, timestamp, message FROM messages WHERE ((receiver='$log_username' AND receiver='$messageOther') OR (sender='$messageOther' AND sender='$log_username')) ORDER BY timestamp DESC