[ecfisa]

Hola.

Código Delphi [-]
procedure TForm1.FormCreate(Sender: TObject);
var
  cb: TComboBox;
begin
  FDQuery1.Close;
  FDQuery1.SQL.Text := 'SELECT ID, NOMBRE FROM VENTAS';
  FDQuery1.Open;
  cb := ComboBox1;
  // Recorrer tabla y guardar nombre e id en el combo
  while not FDQuery1.Eof do
  begin
    cb.Items.AddObject(FDQuery1.FieldByName('MARCA').AsString,
      TObject(FDQuery1.FieldByName('ID').AsInteger));
    FDQuery1.Next;
  end;
end;

procedure TForm1.ComboBox1Change(Sender: TObject);
var
  cb : TComboBox;
  id: Integer;
begin
  cb := TComboBox(Sender);
  id := Integer(cb.Items.Objects[cb.ItemIndex]); // Aquí se obtiene el valor del ID

  ShowMessageFmt('El ID es: %d', [id]);

  if cb.ItemIndex <> -1 then
  begin
    FDQuery1.Close;
    FDQuery1.SQL.Text := 'SELECT * FROM VENTAS WHERE VENDEDOR = :NOMBRE';
    FDQuery1.ParamByName('NOMBRE').AsString := cb.Items[cb.ItemIndex];
    FDQuery1.Open;
  end;
end;

Saludos