คือผมต้องการ..จะเขียน..php เพื่อให้รันห้องสอบอะครับ

$sql = "SELECT roomNo, count(*) as cn  FROM member GROUP BY roomNo ORDER BY roomNo DESC LIMIT 1";
$result = mysql_query($sql);
$row=mysql_fetch_assoc($result);
$roomNo = $row['roomNo'];
if($row['cn'] == 30){
    ++$roomNo;
} 
$sql = "INSERT INTO (memberName, roomNo) VALUES('test', $roomNo)";
mysql_query($sql);