$sql = "DELETE FROM $tbl_session_rel_course_rel_user WHERE id_session='$id_session' AND course_code='$enreg_course' AND id_user='$existing_user'";
$sql = "DELETE FROM $tbl_session_rel_course_rel_user WHERE id_session='$id_session' AND course_code='$enreg_course' AND id_user='$existing_user' AND status != 2 ";