Just a tip, lets say you have a sub_id but the Subject is null in the database and you cannot guarantee that the Subject database field is populated, your table borders will not display correctly (try it and see).
It's a good idea to do something like the following:
echo "<td width='80%'>";
echo empty($row["Subject"]) ? '-' : $row["Subject"]; // If Subject is empty, display a - char else display the value of Subject
Or you can display a space char instead of the '-' char or whatever.