public static function list_competencies($courseid) {
        global $DB;

        $sql = 'SELECT comp.*
                  FROM {' . competency::TABLE . '} comp
                  JOIN {' . self::TABLE . '} coursecomp
                    ON coursecomp.competencyid = comp.id
                 WHERE coursecomp.courseid = ?';
        $params = array($courseid);

        $sql .= ' ORDER BY coursecomp.sortorder ASC';
        $results = $DB->get_recordset_sql($sql, $params);
        $instances = array();
        foreach ($results as $result) {
            $comp = new competency(0, $result);
            $instances[$comp->get('id')] = $comp;
        }
        $results->close();

        return $instances;
    }