code: @Override
     protected int deleteReferenceByOrderNum(String id, int orderNum) throws SQLException, InvalidItemStateException,
        RepositoryException
     {
        if (deleteReferenceByOrderNum == null)
        {
           deleteReferenceByOrderNum = dbConnection.prepareStatement(DELETE_REFERENCE_BY_ORDER_NUM);
        }
        else
        {
           deleteReferenceByOrderNum.clearParameters();
        }
  
        deleteReferenceByOrderNum.setString(1, id);
        deleteReferenceByOrderNum.setInt(2, orderNum);
  
        return executeUpdate(deleteReferenceByOrderNum, TYPE_DELETE_REFERENCE_BY_ORDER_NUM);
     }
docs: {@inheritDoc}