dbutils的count问题

	/**
	 * 根据车次和座位类型获得对应的已订座位数
	 * 
	 * @param id
	 * @return
	 */
	public Long countOrderedSeat(int scheduleID, int seatType) {
		// count(Type)返回的是Long类型,无奈
		Long retVal = null;
		String sql = " select count(Type) from tb_train_seat  where Type=? "
                                + " and tb_train_seat.TrainID=("
				+ " select TrainID from tb_train_schedule where AutoID=?)";

		Object[] params = { seatType, scheduleID };
		try {
			retVal = (Long) super.findOnly(sql, params);
		} catch (Exception e) {
			log.error("根据车次和座位类型获得对应的已订座位数出错:", e);
		}
		return retVal;
	}