ทำไมถึงทำการแทรก sql select ระหว่างกลางไม่ได้ครับ

<?PHP
$sql = "SELECT * FROM users WHERE user_id = '$seller' order by id asc";
$result = mysql_query($sql);
$datas=mysql_fetch_array($result);{
$username = stripslashes(str_replace('\r\n', '<br>',($datas['username'])));
}
?>

<?PHP

$reload = $_SERVER['PHP_SELF']."?update_to=".$_GET['update_to'];
$rpp = 20; // results per page
$adjacents = 4;
$page = intval($_GET["page"]);
if(!$page) $page = 1;

$sql="SELECT * FROM payments LEFT JOIN host_details ON payments.id=host_details.id 
                             LEFT JOIN billing_details ON host_details.id=billing_details.id
WHERE payments.buyer = '$user_id' AND payments.payment_status = 'Completed' AND billing_details.type = 'details' order by $_GET[update_to] ";



$result = mysql_query($sql);
$tcount = mysql_num_rows($result);
$tpages = ($tcount) ? ceil($tcount/$rpp) : 1;
$count = 0;
$i = ($page-1)*$rpp;
?>

<ul class="item-list">

<?PHP
$number = 0;

while(($count<$rpp) && ($i<$tcount)) 
    {

     $number++;

     mysql_data_seek($result,$i);
     $datas=mysql_fetch_array($result);
        {
          $id_payment = stripslashes(str_replace('\r\n', '<br>',($datas['id_payment'])));
          $seller = stripslashes(str_replace('\r\n', '<br>',($datas['seller'])));
          $img_path = stripslashes(str_replace('\r\n', '<br>',($datas['img_path'])));
?>

<?PHP
$sql = "SELECT * FROM users WHERE user_id = '$seller' order by id asc";
$result = mysql_query($sql);
$datas=mysql_fetch_array($result);{
$username = stripslashes(str_replace('\r\n', '<br>',($datas['username'])));
}
?>


<?PHP echo $username; ?>

<?PHP
        }
    $i++;
    $count++;
     }
?>