ช่วยดูโค๊ด การ SELECT หลายตาราง แต่อยากจะตัดตัวที่ ซ้ำกันออกไปครับ

$id_plan=$result['id_plan']; 
     	$sql2="select  * from inspection, request, corporation WHERE inspection.id_request=request.id_request AND request.id_corparation=corporation.id_corparation AND request.id_plan='$id_plan' AND id_teacher='$id_teacher' ";
		$dbquery2=mysql_db_query($dbname, $sql2);
		$i=1;
		while($result2=mysql_fetch_array($dbquery2))
		{	
									
			if($bg == "#DFE6F1") { //ส่วนของการ สลับสี 
			$bg = "#FFFFFF";
			} else {
			$bg = "#DFE6F1";
			}
?>
						<tr class='text' bgcolor='<?= $bg; ?>'>
						<td align='center'><?= $i; ?></td>
						<td align="left">&nbsp;<?= $result2['co_fullname']; ?></td>
						<td align="center">

<?  	
		$id_request=$result2['id_request'];
		$sql3="SELECT * FROM inspection WHERE 			id_request='$id_request' AND id_teacher='$id_teacher' ";	
		$dbquery3=mysql_db_query($dbname, $sql3);
		$num_rows3=mysql_num_rows($dbquery3);
		?><?= $num_rows3; ?></td>
						<td align='center'><a href='ins_formdetail.php?id_request=<?= $result2['id_request'] ?>' class='textnormal'>รายละเอียด</a></td>
					</tr>
                    <?
					$i++;
				}
				  	?>