ผมอยากถามปัญหาเกี่ยวกับเรื่อง Query กับ While loop ครับ

<table width=100%>
<TR  bgcolor='#FFCCCC'>
	<TD width=40 align=center rowspan=2><B>ที่</B></TD>
	<TD width=100 align=center rowspan=2><B>รหัสประจำตัว</B></TD>
	<TD align=center rowspan=2><B>ชื่อ - สกุล</B></TD>
	<TD width=40 align=center rowspan=2><B>เลขที่</B></TD>
	<td align=center rowspan=2><b>ห้อง</b></td>
	<?php 

			$SQL2 = "SELECT sub_code from student_subject where std_class='$class' and room = '$room'";
			$c = $db->prepare($SQL2);
			$c->execute();
			$count_sub = $c->rowCount();
			?>
		<TD align=center colspan=32><B>รหัสวิชา</B></TD>
		<tr bgcolor='#FFCCCC'>
			<?php
			while($row = $c->fetch()){
				$sub = $row['sub_code'];
			echo "<td>$sub</td>";
			}
			 ?>
			
		</tr>
		<?php  //
	$sql=$sql." ORDER BY student_main.id  LIMIT $start,$pagelen";
	$dbquery = $db->prepare($sql);
	$dbquery->execute();
	$M=1;
		$N=(($page-1)*$pagelen)+1;
	if($count_sub !== 0){

		While ($result = $dbquery->fetch()){
			$color=(($M%2) == 0)?" class='even'":" class='odd'";
			#$color=($result[status]==0)?"  class='out'":$color;
			$room=$result['room'];
			echo"<TR $color>
				<TD align=right>$N</TD>
				<TD align=center>$result[student_id]<INPUT TYPE=hidden name=student_id[] value=$result[student_id]></TD>
				<TD><B>$result[prename] $result[name]  $result[surname]</B></TD>
						<TD align=center>$result[student_number]</TD>
				<td align=center>$room</td>";
				
			$sql_val = "SELECT * from student_inclass_main inner join student_subject on (student_inclass_main.class_now=student_subject.std_class) where month(check_date) = $_REQUEST[month] and class_now=$class and room_now=$room and student_check_year='$year_active' and student_id=$result[student_id] and sub_code='$sub'";
		
			$query_val = $db->prepare($sql_val);
			$query_val->execute();
		
			for($t=0;$t<=$count_sub;$t++){
				$Lnums[$t]=0;
			}

			while($rs = $query_val->fetch()){
				$tmp = array();
				$tmp=explode(",",$rs['check_val']);
				for($cTmp=0;$cTmp<count($tmp);$cTmp++){
					$tmpC=explode(":",$tmp[$cTmp]);
					@$Lnums[$cTmp]=($tmpC[1]!="C" && $tmpC[1]!="T")?$Lnums[$cTmp]+1:$Lnums[$cTmp]+0;

				}
			}
			for($t=0;$t<$count_sub;$t++){
				echo "<td>$Lnums[$t]</td>";

			}

		}
				
$M++;
			$N++;
		
			}
		}else{
			
		}
		echo "</table>";
 ?>
<script>
function goto_url(val){
	if(val==0){
		callfrm("?option=report_table");   // page ย้อนกลับ 
	}else if(val==1){
		 if(frm1.class_now.value == ""){
			alert("กรุณาเลือกชั้น");
		}else if(frm1.part.value == ""){
			alert("กรุณาเลือกภาคเรียน");
		}else if(frm1.month.value == ""){
			alert("กรุณาเลือกเดือน");
		}else{
			callfrm("?option=report_table&index=1");   //page ประมวลผล
		}
	}
}

</script>