Subform issue ms access vba

Question

I am writing because I faced very time consuming issue I have not yet solved. It is connected with ms access query and form data exchange. To put it in a simple way. I have the following form: Form

I have table with cars and inside it columns in the order as shown in the Q_Cars query. I have also subform which is updated using particular comboboxes (currently two assigned) which are updating query using VBA code (requery option). However it works only if I pick values for both comboboxes only. Can you help me to find a way to put ia query criteria criterion which for an empty combobox will run query with all available data? I tried to use eg the following structure inside criteria in query form:

IIf( Formularze![Form]![T_id] <>""; «Wyr» Formularze![Form]![T_id] ;>0)

Or other attempts with isempty, isnull function but without success. Do you know how to solve this issue? In my version due to language "," is replaced with ";" inside if structure. Remaining code:

Private Sub btn_clear_Click()
Me.T_brand.Value = ""
Me.T_id.Value = ""
Me.T_color = ""
Me.T_seats = ""
Q_Cars_subform.Requery
End Sub
Private Sub T_brand_AfterUpdate()
Q_Cars_subform.Requery
End Sub
Private Sub T_id_AfterUpdate()
Q_Cars_subform.Requery
End Sub

and table table Regards, Peter

Query code:

SELECT Cars.car_id, Cars.car_brand, Cars.car_color, Cars.car_seats
FROM Cars
WHERE (((Cars.car_id)=IIf(Formularze!Form!T_id<>"","«Wyr» Formularze![Form]![T_id] ",(Cars.car_id)>0)) And ((Cars.car_brand)=Formularze!Form!T_brand));

Answer 1

That IIF contains invalid code.

You can just use a logical OR statement in your WHERE criterium, no need for IIF .

Try the following:

SELECT Cars.car_id, Cars.car_brand, Cars.car_color, Cars.car_seats
FROM Cars
WHERE (Cars.car_id = Formularze![Form]![T_id] OR Nz(Formularze![Form]![T_id]) = "") 
AND (Cars.car_brand = Formularze!Form!T_brand OR NZ(Formularze!Form!T_brand) = "");

Note that this will show everything if both are empty, I can adjust it to show nothing in that case if needed.