MS Access Complex Query Help (Cross-Join typ) - sql

Question

Greetings: I am working on a variant configurator for a part numbering system.
I have two tables which define the characteristics of the numbering system. Null means the combination is invalid and to be skipped.
Table 1:
PowerSize | Model A | Model B | Model... | Input A | Input B | Input... | Temp A | Temp B | Temp... |
20HP | S10 | S30 | null | 6P | null | 5R | 40C | 50C | null|
200HP |null|null| E10 | 6P | 3R | null | null | 50C | 55C|
**Table 2:**
Model | Normal Duty | Heavy Duty | Light Duty | No Filter | Sine Filter |
S10 | N | null | null | N | S |
S30 | null | H | null | N | null |
E10 | null | null | L | null | S |
I need a query (or series of queries) that explodes the valid combinations:
**Result Example**
**Model | PowerSize | Input | Temp | Duty | Filter |**
S10 | 20HP | 6P | 40C | N | N |
S10 | 20HP | 6P | 40C | N | S |
S10 | 20HP | 6P | 50C | N | N |
S10 | 20HP | 6P | 50C | N | S |
S10 | 20HP | 5R | 40C | N | N |
S10 | 20HP | 5R | 40C | N | S |
S10 | 20HP | 5R | 50C | N | N |
S10 | 20HP | 5R | 50C | N | S |
S30 | 20HP | 6P | 40C | H | N |
S30 | 20HP | 5R | 40C | H | N |
S30 | 20HP | 6P | 50C | H | N |
S30 | 20HP | 5R | 50C | H | N |
E10 | 200HP | 6P | 50C | L | S |
E10 | 200HP | 3R | 50C | L | S |
E10 | 200HP | 6P | 55C | L | S |
E10 | 200HP | 3R | 55C | L | S |
and so forth.
I tried using Dlookup but wasn't able to sort it out.
I tried DLookup but it didn't handle the null's as exclusions (at least I couldn't figure out how to do the criteria for it to work)
Can someone give me some pointers or examples? Greatly appreciated in advance.

Answer 1

use null check, example : Not IsNull(DLookup(

Answer 2

I built a VBA script using two loops to build a set of union queries based on a auxiliary table containing all fields, and then manually joined each union query to create the completed list (about 50,000 lines long). Performance is good this way, much better than DLookup methods I had tried. If I had to do it over again, I may have setup SQL Express and used unpivot or cross join for this workflow as that probably would have been less time consuming than researching alternative ways and eventually writing and testing a VBA routine.
Dim aux_table, main_table, query_sort_name, main_table_catsource, str_query_category_subloop, str_query_category_union As String
'Define Name
aux_table = "AuxTable_Series"
main_table = "VC3_Series_vs_Input_Duty_Env_Filter_DBR_Cert"
main_table_catsource = "VSD_Series"
query_sort_name = "autoqry_Series_"
'Load Aux_table to recordset
Set rs_AuxTable = CurrentDb.OpenRecordset(aux_table)
'Loop through each Aux Table Column/Field
For Each aux_field In rs_AuxTable.Fields
'Set Aux Column Name
'MsgBox aux_field.Name
'Get Count of Records for Column
Set rs_count = CurrentDb.OpenRecordset("SELECT COUNT(" & aux_field.Name & ") AS RecCount FROM " & aux_table)
'MsgBox rs_count.reccount
rs_AuxTable.MoveFirst
i = 0
str_query_category_union = ""
Do While i < rs_count.reccount
'MsgBox rs_AuxTable.Fields(aux_field.Name)
'Same Category Union Query
str_query_category_subloop = "SELECT " & main_table & "." & main_table_catsource & "," & main_table & "." _
& rs_AuxTable.Fields(aux_field.Name) & " AS " & aux_field.Name & " FROM " & main_table & " WHERE " _
& main_table & "." & rs_AuxTable.Fields(aux_field.Name) & " Is Not Null"
'MsgBox rs_AuxTable.Fields(aux_field.Name)
If i = 0 Then
str_query_category_union = str_query_category_subloop
Else
str_query_category_union = str_query_category_union & " UNION " & str_query_category_subloop
End If
rs_AuxTable.MoveNext
i = i + 1
Loop
rs_AuxTable.MoveFirst
i = 0
'MsgBox str_query_category_union
CurrentDb.CreateQueryDef query_sort_name & aux_field.Name, str_query_category_union
Next
rs_AuxTable.Close
rs_count.Close
Set rs_AuxTable = Nothing
Set rs_count = Nothing
Set aux_field = Nothing
End Sub