LEFT JOIN $tbl_session_rel_course_user cu on u.user_id = cu.id_user and course_code='".api_get_course_id()."' AND id_session ='".api_get_session_id()."'
LEFT JOIN $tbl_session_rel_course_user cu on u.user_id = cu.id_user and course_code='".api_get_course_id()."' AND id_session ='".api_get_session_id()."'