Access 2013 ComboBox based on Combobox with Junction Table - combobox

Question

Good day. I would like to know why a Parameter Request pops up when executing a query. I have a form with 2 comboboxes where the 2nd one depends on the value in the 1st one. I do know how to do this when it involves 2 tables. I am having trouble when there is a many to many relationship.
Table 1: name - Supply_Sources, fields - Source_ID(pk), SupplySourceName
Table 2: name - Warehouse_Locations, fields - WLocation_ID(pk), Location_Name
Table 3 (junction): name - SupplySource_WarehouseLocation, fields - Supply_Source_ID(pk), Location_In_ID(pk)
On my form frmInventoryReceivedInput I have cboSupplySource and cboWLocation.
I populate cboSupplySource with
SELECT [Supply_Sources].[Source_ID], [Supply_Sources].[SupplySourceName] FROM Supply_Sources;
I am trying to get a drop down list in the cboWLocation based on the value in cboSupplySource. I am wanting to see the location names of where the supplies are placed in the warehouse.
I have a requery in cboSupplySource After Update (with cboWLocation as the control name). The SQL that I have come up with so far is:
SELECT Warehouse_Locations.Location_Name,
SupplySource_WarehouseLocation.Supply_Source_ID,
SupplySource_WarehouseLocation.Location_In_ID
FROM Warehouse_Locations RIGHT JOIN (Supply_Sources LEFT JOIN
SupplySource_WarehouseLocation ON Supply_Sources.Source_ID =
SupplySource_WarehouseLocation.Supply_Source_ID) ON
Warehouse_Locations.WLocation_ID =
SupplySource_WarehouseLocation.Location_In_ID
WHERE (((Warehouse_Locations.Location_Name)=[frmInventoryReceivedInput].[cboSupplySource]));
When it runs, on tabbing out of cboSupplySource, Enter Parameter Value dialogue box pops up, looking for frmInventoryReceivedInput.cboSupplySource input. Nothing I input brings up the correct list in cboWLocation.
Obviously, I do not have the correct select statement. Any help would be appreciated.

Answer 1

For cboWLocation try the recordSource query:
SELECT Warehouse_Locations.Location_Name
FROM Warehouse_Locations INNER JOIN (Supply_Sources INNER JOIN
SupplySource_WarehouseLocation ON Supply_Sources.Source_ID =
SupplySource_WarehouseLocation.Supply_Source_ID) ON
Warehouse_Locations.WLocation_ID =
SupplySource_WarehouseLocation.Location_In_ID
WHERE ((Supply_Sources.SupplySourceName)=([Forms]![frmInventoryReceivedInput].[cboSupplySource]))
Be aware, that the combobox columns have to be set to columncount 1 in this case with appropriate column width, because you said you only want to see the location names. Further, you should be sure that cboWLocation is not bound to a Control Source, to not overwrite anything.
You can apply it in VBA at the cboWLocation Enter Event.
In the following code example, the combobox cboWLocation is only updated, if there is a value in combobox cboSupplySource.
Private Sub cboWLocation_Enter()
If not (isNull(Me!cboSupplySource) Or Me!cboSupplySource.ListIndex = -1) then
Me.cboWLocation.RowSource = strSQL 'Put here the previous mentioned SQLString
End if
End Sub
HINT: It would be better for performance, when you change the bound column in cboSupplySource to the PK SourceID instead of the name. (With two columns in combobox cboSupplySource) Then use this PK to compare in your WHERE statement instead of the name. this is what keys in tables are for.
Edit: In the WHERE statement, maybe you have to put the namecomparison between ' ' because it is a string