mysql error

[Pino]

 $query="SELECT * FROM clients WHERE username='$username'";
        $result=mysql_query($query);
        $num=mysql_numrows($result);
        
        $i=0;
        
        while($i < $num) 
        {
        $msg=mysql_result($result,$i,"msg");
        
        echo $msg;
        
        ++$i
        } 

anyone see any problems? i am connected to the DB