// find, if any, the column of 'table' whose name is 'columnName'
  private DbORColumn findColumn(DbORTable table, String columnName) throws DbException {
    DbORColumn namedColumn = null;
    DbRelationN relN = table.getComponents();
    DbEnumeration enu = relN.elements(DbORColumn.metaClass);
    while (enu.hasMoreElements()) {
      DbORColumn c = (DbORColumn) enu.nextElement();
      if (columnName.equals(c.getName())) {
        namedColumn = c;
        break;
      }
    } // end while
    enu.close();

    return namedColumn;
  }