ขอสอบถามวิธีการ Query หน่อยครับ มันค่อนข้างกิน CPU มากเลย ดู Query ข้างในครับ

<?php
$term = isset($_GET['term']) ? $_GET['term'] : '';
$years = isset($_GET['years']) ? $_GET['years'] : '';
$groups_id = isset($_GET['groups_id']) ? $_GET['groups_id'] : '';

$groups_name = '';
if($groups_id == '1'){
	$groups_name = 'ภาคปกติ';
}else{
	$groups_name = 'ภาค กศ.บป.';
}

include 'var/db_conn.inc.php';

$sql_fac = "
SELECT
    FacID, FacName
FROM
    FacSchool
ORDER BY 
    FacID ASC;
                ";
$param = array();
$query = $conn->prepare($sql_fac);
$query->execute($param);
while($rs = $query->fetch(PDO::FETCH_ASSOC)){
?>
	<b>
		<?=$rs["FacName"];?>
	</b>
	<?php
	$sql_DepSchool = "
SELECT
    d.DepID, d.DepName
FROM
    DepSchool d
WHERE
    d.FacID = :fac_id
ORDER BY
    d.DepName ASC
	";
	$param2 = array(":fac_id"=>$rs["FacID"]);
	$query2 = $conn->prepare($sql_DepSchool);
	$query2->execute($param2)
	while($rs2 = $query2->fetch(PDO::FETCH_ASSOC)){
	?>
	<table border="1" width="100%" cellspacing="1" cellpadding="0">
		<tr>
			<td colspan="8" align="center"><?php echo $rs2["DepName"];?></td>
		</tr>
		<tr>
			<td align="center">ที่</td>
			<td align="center">รหัสวิชา</td>
			<td align="center">ชื่อวิชา</td>
			<td align="center">หน่วยกิต</td>
			<td align="center">จำนวนนักศึกษา</td>
		</tr>
		<?php
        $sql_ftes = "
SELECT
    d.DepName, s.SubID, s.SubName, s.Credit, 
    COUNT(r.ID) AS Total
FROM
    RegSchool r
INNER JOIN RegDetailSchool rd ON r.RID = rd.RID
INNER JOIN SubSchool s ON s.RefID = rd.RefID
INNER JOIN DepSchool d ON d.DepID = s.DepID
INNER JOIN FacSchool f ON f.FacID = d.FacID
WHERE
    d.DepID = :dep_id
    AND r.Term = :term
    AND r.Years = :years
    AND rd.GID = :g_id
GROUP BY
    s.SubName, s.Credit, d.DepName, s.SubID
ORDER BY
    s.SubName ASC
                    ";
		$param3 = array(":dep_id"=>$rs2["DepID"], ":term"=>$term, ":years"=>$years, ":g_id"=>$groups_id);
		$query3 = $conn->prepare($sql_ftes);
		$query3->execute($param3)
		
		$sch = 0;
		$sum_sch = 0;
		$ftes = 0;
		$sum_ftes = 0;
		$rate = 0;
		$sum_rate = 0;
		$count = 0;
		while($rs3 = $query3->fetch(PDO::FETCH_ASSOC)){
			$count++;
			$sch = cal_sch($rs3["Credit"], $rs3["Total"]);
			$ftes = cal_ftes($sch);
			$rate = cal_rate($ftes);

			$sum_sch += $sch;
			$sum_ftes += $ftes;
			$sum_rate += $rate;
		?>
		<tr>
			<td><?php echo $count;?></td>
			<td><?php echo $rs3["SubID"];?></td>
			<td><?php echo $rs3["SubName"];?></td>
			<td><?php echo $rs3["Credit"];?></td>
			<td><?php echo $rs3["Total"];?></td>
		</tr>
		<?php
		}
		?>
	</table>
	<br/>
	<?php
	}
	?>
	<br/>
<?php
}
?>