How to select latest change done in the given Table structure?

I have a Table structure as id, trackid, table_name, operation, oldvalue, newvalue, field, changedonetime

Now if I have 3 rows for the same "trackid" same "field", then how can i select the latest out of the three?

i.e. for e.g.:

id = 100 trackid = 152 table_name = jos_menu operation= UPDATE oldvalue = IPL newvalue = IPLcccc field = name live = 0 changedonetime = 2010-04-30 17:54:39

and

id = 101 trackid = 152 table_name = jos_menu operation= UPDATE oldvalue = IPLcccc newvalue = IPL2222 field = name live = 0 changedonetime = 2010-04-30 18:54:39

As u can see above the secind entry is the latest change, Now what query I shoud use to get the only one and Latest row out of many such rows...

UPDATED

$distupdqry = "select DISTINCT trackid,table_name from jos_audittrail where live = 0 AND operation = 'UPDATE'";
$disupdsel = mysql_query($distupdqry);
$t_ids = array();
$t_table = array();
while($row3 = mysql_fetch_array($disupdsel))
{   
    $t_ids[] = $row3['trackid'];
    $t_table[] = $row3['table_name'];
    //$t_table[] = $row3['table_name'];
}

//echo "<pre>";print_r($t_table);echo "<pre>";

//exit;
for($n=0;$n<count($t_ids);$n++)
{

      $qupd = "SELECT * FROM jos_audittrail WHERE operation = 'UPDATE'  AND trackid=$t_ids[$n] order by changedone DESC ";
    $seletupdaudit = mysql_query($qupd);
    $row4 = array();
    $audit3 = array();
    while($row4 = mysql_fetch_array($seletupdaudit))
    {   
        $audit3[] = $row4;  
    }           


        $updatefield = '';
        for($j=0;$j<count($audit3);$j++)
        {
            if($j == 0)
            {

                if($audit3[$j]['operation'] == "UPDATE")
                {
                            //$insqry .= $audit2[$i]['operation']." ";
                            //echo "<br>";
                    $updatefield .= "UPDATE `".$audit3[$j]['table_name']."` SET ";

                }
            }

            if($audit3[$j]['operation'] == "UPDATE")
            {

                $updatefield .= $audit3[$j]['field']." = '".$audit3[$j]['newvalue']."', ";

            }

        }
        /*echo "<pre>";
    print_r($audit3);
    exit;*/
        $primarykey = "SHOW INDEXES FROM `".$t_table[$n]."` WHERE Key_name = 'PRIMARY'";
        $prime = mysql_query($primarykey);
        $pkey = mysql_fetch_array($prime);
        $updatefield .= "]";
        echo $updatefield = str_开发者_如何学编程replace(", ]"," WHERE ".$pkey['Column_name']." = '".$t_ids[$n]."'",$updatefield);   
}

Here I am creating the Update query by fetching the records from the initially described table which is here mentioned as audittrail table... please go throught the code.. and see how can i make the required change i need finally..

select * from TableName order by id DESC LIMIT 1

EDITED. YEs you can if you want to order by "changedonetime" USE.

select * from TableName order by changedonetime DESC LIMIT 1