I don't know why but the data type in this code makes a trouble when the id in the url starts with the number zero like this: http://localhost/exp/update.php?id=03A43 In this case the id is 03A43.

And my query looks like this:

mysql_select_db("school", $con);
   $result = mysql_query("SELECT * FROM student WHERE IDNO=".(int)$_GET['id']);

?>  

There is no problem in the design if the id does not start with the number zero. What might be the proper data type for numbers beginning in zero?