//昇順
procedure TForm1.N3Click(Sender: TObject);
var
  FN : string;
begin
  FN := DBGrid1.SelectedField.FieldName;
  with  Query1  do
  begin
    Active := False;
    SQL[1] := 'ORDER BY ' + FN ;
    Active := True;
  end;
end;

//降順
procedure TForm1.N4Click(Sender: TObject);
var
  FN : string;
begin
  FN := DBGrid1.SelectedField.FieldName;
  with  Query1  do
  begin
    Active := False;
    SQL[1] := 'ORDER BY ' + FN + ' DESC';
    Active := True;
  end;
end;