Estaba convencido de que se podia
Código Delphi
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procedure TForm1.Button1Click(Sender: TObject);
begin
ADOQuery1.Close;
if Edit1.Text <> '' then
ADOQuery1.Parameters.ParamByName('ParamId').Value := Edit1.Text
else
ADOQuery1.Parameters.ParamByName('ParamId').Value := NULL;
ADOQuery1.Open;
end;
procedure TForm1.FormCreate(Sender: TObject);
begin
ADOQuery1.SQL.Text := ' SELECT * FROM Productos WHERE Id = IsNull(:ParamId, Id) ';
ADOQuery1.Prepared := True;
end;
Saludos