//只要前五条记录procedure TForm1.Button1Click(Sender: TObject);begin  with ADODataSet1 do begin    Close;    CommandText := 'SELECT TOP 5 * FROM country';    Open;  end;end;//去除重复procedure TForm1.Button2Click(Sender: TObject);begin  with ADODataSet1 do begin    Close;    CommandText := 'SELECT DISTINCTROW * FROM country';    Open;  end;end;//获取字段列表procedure TForm1.Button3Click(Sender: TObject);var  i: Integer;  str: string;begin  str := '';  for i := 0 to ADODataSet1.FieldDefs.Count - 1 do  begin    str := str + ADODataSet1.FieldDefs[i].Name + sLineBreak;  end;  ShowMessage(str);end;