ช่วยด้วยครับ ออกรายงายยอดขายตามเดือน ครับ แต่ยอดขายออกมาหมดเลยครับ

<?php
/*
 * include file start***********************************************************
 */
require 'library/pagination.php';
/*
 * php code///////////**********************************************************
 */
$title = 'ระบบจัดการร้านค้า : รายงานยอดขาย';
$db = new database();
$pagination = new Zebra_Pagination();

$sql_pd ="select b.id,b.name,SUM(a.quantity) as dsumOrder,a.price,(SUM(a.quantity) * a.price) as gndSum ";
$sql_pd .="from order_details a,products b ";
$sql_pd .="where a.product_id=b.id GROUP by b.id  ";

$query_pd = $db->query($sql_pd);
$rows_pd = $db->rows($query_pd);

$per_page = 20;
$page_start = (($pagination->get_page() - 1) * $per_page);
$sql_pd .= "ORDER BY dsumOrder DESC LIMIT {$page_start},{$per_page} ";
$pagination->records($rows_pd);
$pagination->records_per_page($per_page);
$pagination->base_url('', FALSE);
$query_pd_page = $db->query($sql_pd);

$page = ($page_start!=0) ? $page_start : "1";
$pages = ceil($rows_pd/$per_page);

$uri = $_SERVER['REQUEST_URI']; // url

/*
 * php code///////////**********************************************************
 */

/*
 * header***********************************************************************
 */
require 'template/back/header.php';
/*
 * header***********************************************************************
 */
?>
<title>รายงานยอดขายสินค้า</title>


<div id="page-warpper"> 
  <div id="divprint"> 
    <div class="row">
        <div class="col-lg-12">
            <h2 class="page-header">รายงานยอดขายสินค้า</h2>
        </div>
    </div>
    <div class="row">
        <div class="col-lg-12">

        </div>
    </div>
    <div class="row">
        <div class="col-lg-12">           
            <div id="user-grid" class="grid-view">
                <!--<div class="summary">หน้า <?php //echo $page;?> จากทั้งหมด <?php //echo $pages; ?> หน้า</div> -->
                <table class="table table-striped table-custom">
                    <thead>
                        <tr>
                            <th id="user-grid_c0">
                                ลำดับ
                            </th>
                            <th id="user-grid_c1">
                                รหัสสินค้า
                            </th>
							<th id="user-grid_c1">
                                สินค้า
                            </th>
                            <th id="user-grid_c2">
                                ราคาต่อหน่วย
                            </th>
                            <th id="user-grid_c4">
                                จำนวน
                            </th>
							<th id="user-grid_c5">
                                รวม
                            </th>                            
                        </tr>
                    </thead>
                    <tbody>
                    
                        <?php
                        $i = 0;
						$SumOrder=0;
						$SumTotal=0;  
						
                        while ($rs_pd = $db->get($query_pd_page)) {
                            $i++;
							
							$SumOrder=$SumOrder+$rs_pd['dsumOrder'];
							$SumTotal=$SumTotal+$rs_pd['gndSum'];
							
							$tr = ($i % 2 == 0) ? "odd" : "even";
                            ?>
                            <tr class="<?php echo $tr; ?>">
                                <td><?php echo $i ?></td>
                                <td><?php echo $rs_pd['id']; ?></td>
								<td><?php echo $rs_pd['name']; ?></td>
								<td><?php echo number_format($rs_pd['price'],2); ?></td>
                                <td><?php echo $rs_pd['dsumOrder']; ?></td>                                
                                <td><?php echo number_format($rs_pd['gndSum'],2); ?></td>                                                                
                            </tr>
                        <?php } ?>
                    </tbody>
					                    <tfoot>
                        <tr>
                            <th id="user-grid_c0">
                               
                            </th>
							<th id="user-grid_c1">
                                 
                            </th>
                            <th id="user-grid_c2">
                                <?php  echo "รวมทั้งหมด" ?>
                            </th>
                            <th id="user-grid_c3">
                                <?php echo $SumOrder; ?>
                            </th>
							<th id="user-grid_c4">
                                <?php echo number_format($SumTotal,2); ?>                                
                            </th>                            
                        </tr>
                    </tfoot>
                </table>
                <div>
                    <?php $pagination->render(); ?>
                </div>
            </div>
        </div>
    </div>
	<div>

<div class="summary">หน้า <?php echo $page;?> จากทั้งหมด <?php echo $pages; ?> หน้า</div>
<!-- <button type="button" class="btn btn-default" onClick="printDiv('divprint')"><span class="glyphicon glyphicon-print"></span> พิมพ์รายงาน</button> -->

	</div>
	
    <script type="text/javascript">
        $(document).ready(function () {
            $('.search-button').click(function () {
                $('.search-form').toggle();
                return false;
            });
        });
    </script>
	<script type="text/javascript">
		function printDiv(divName) {
			 var printContents = document.getElementById(divName).innerHTML;
			 var originalContents = document.body.innerHTML;
		
			 document.body.innerHTML = printContents;
			 window.print();
		
			 document.body.innerHTML = originalContents;
		}
</script>
  </div>
  <br>
  <button type="button" class="btn btn-default" onClick="printDiv('divprint')"><span class="glyphicon glyphicon-print"></span> พิมพ์รายงาน</button>
</div> 

<?php
/*
 * footer***********************************************************************
 */
require 'template/back/footer.php';
/*
 * footer***********************************************************************
 */
mysql_close();

?>