code: public DataColumns getDataColumn(String tableName, String columnName)
  			throws SQLException {
  		TableColumnKey id = new TableColumnKey(tableName, columnName);
  		return queryForId(id);
  	}
docs: Get DataColumn by column name and table name
  
  @param tableName
  table name to query for
  @param columnName
  column name to query for
  @return DataColumns
  @throws SQLException
  upon failure