code: public OqlBuilder<T> orderBy(final int index, final String orderBy) {
      if (null != orders) {
        if (isNotEmpty(statement)) { throw new RuntimeException("cannot add order by to a exists statement."); }
        this.orders.addAll(index, Order.parse(orderBy));
      }
      return this;
    }
docs: 指定排序字符串的位置
  
  @param index 从0开始
  @param orderBy 排序字符串
  @return 查询构建器