Count นับจำนวนใน loop ดึงข้อมูลให้ออกมาแสดงแบบรูปนี้ต้องทำยังไงครับ

echo "<table>
	<tr>
		<td><b>example loop</b></td>
	</tr>";
$sql = "select c.course_id, c.course_name, s.subject_id, s.subject_name, s.subject_detail 
	from tb_course c inner join tb_subject s on c.course_id = s.ref_course_id 
	order by c.sourse_name asc";
$chkcourse = ""; 
$rs = mysql_query($sql);
while($rows = mysql_fetch_array($rs))
{
	$course_name = $rows["course_name"];
	$subject_name = $rows["subject_name"];
	if($chkcourse != $course_name){
		echo "<tr><td><b>".$course_name."</b></td></tr>";
		$chkcourse = $course_name;
	}
	echo "<tr><td>".$subject_name."</td></tr>";
}
echo "</table>";