procedure TForm1.ComboBox1Change(Sender: TObject);
var
cb : TComboBox;
begin
cb := TComboBox(Sender);
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;