为什么会这样的。初学者

unit Unit1;
interface
uses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs, Grids, DBGrids, DB, ADODB;
type TForm1 = class(TForm) ADOConnection1: TADOConnection; ADOQuery1: TADOQuery; DataSource1: TDataSource; DBGrid1: TDBGrid;procedure TForm1.Button1Click(Sender: TObject);beginADOQuery.Close;ADOQuery.SQL.Clear;ADOQuery.SQL.Add('select * from zd_ry ');ADOQuery.Open;end;var Form1: TForm1;
implementation
{$R *.dfm}
end.