ttable生成dbf文件时报错的问题

在createtable是报错（'invalid parameter'）with table_firstpage do
  begin
    Close;
    Active :=False;
    DisableControls;
    DatabaseName:='D:\aa';
    TableName:='N041.dbf';
    TableType :=ttDBase;
    FieldDefs.Clear;
    IndexDefs.Clear;
  end;
  with ado_tmp do
  begin
    close;
    sql.Text := 'select column_name, column_id, data_type from all_tab_columns '#13#10+
                'where table_name=upper(''t_bafirstpage'')  order by column_id ';
    open;
    while not eof do
    begin
      if Fields[2].AsString = 'number' then
        table_firstpage.FieldDefs.Add(Fields[0].AsString,ftInteger,0,True)
      else if Fields[2].AsString = 'varchar2' then
        table_firstpage.FieldDefs.Add(Fields[0].AsString,ftString,0,True);
      next;
    end;
  end;
  table_firstpage.createtable;
  table_firstpage.active := true;