code: @Override
      public TableIdx getJoinTableIdx(final SQLSelect _sqlSelect)
          throws EFapsException
      {
          final String linktoColName = this.attribute.getSqlColNames().get(0);
          final String tableName = ((SQLTable) getTable()).getSqlTable();
          final Attribute joinAttr = this.attribute.getLink().getAttribute("ID");
          final String joinTableName = joinAttr.getTable().getSqlTable();
          return _sqlSelect.getIndexer().getTableIdx(joinTableName, tableName, linktoColName);
      }
docs: Gets the join table idx.
  
  @param _sqlSelect the sql select
  @return the join table idx
  @throws EFapsException the e faps exception