code: public SchemaColumn find(String tableName, String tableAlias,
              String columnName, String columnAlias) {
          SchemaColumn col = new SchemaColumn(tableName, tableAlias,
                  columnName, columnAlias);
          int index = findIndexOfColumn(col);
          if (index != -1) {
              return m_columns.get(index);
          }
          return null;
      }
docs: Retrieve the SchemaColumn that matches the provided arguments.
  @param tableName The table name of the desired column.
  @param tableAlias The table alias of the desired column.
  @param columnName The column name of the desired column.
  @param columnAlias The column alias of the desired column.
  @return The matching SchemaColumn.  Returns null if the column wasn't
  found.