$sql = "SELECT COUNT(DISTINCT(user_id)) AS number FROM $user_table WHERE status = ".intval(Database::escape_string($status))." ";
if (isset ($category_code))
{
if (isset ($category_code)) {
$sql = "SELECT COUNT(DISTINCT(cu.user_id)) AS number FROM $course_user_table cu, $course_table c WHERE cu.status = ".intval(Database::escape_string($status))." AND c.code = cu.course_code AND c.category_code = '".Database::escape_string($category_code)."' ";