Steps for Creating Multiple Step Joins on Different Keys

[MarkDGaal]

I have two tables, Table 1; always has the full detail:

Location | Category 1 | Category 2 | Category 3 | Category 4 | Hours
WAC      | Plane      |Civil       | Recon      | Air        |  1000
WAC      | Plane      | Military   | Patrol     | Land       |  1000
WAC      | Plane      | Civil      |Survey      |Water       |  1000

Table 2 sometime has the full detail and sometimes it does not and never has the "Hours" field:

ID#| Location | Category 1 | Category 2 | Category 3 | Category 4
001| WAC      | Plane      | Civil      | Recon      | Air            
002| WAC      | Plane      | Civil      | Recon      | Air                    
003| WAC      | Plane      | Military   | Patrol     |            
004| WAC      | Plane      | Civil      |            |

*at minimum Table2 always has a match to Table1 based on Location and Category1

I want to create a multiple step join in which the first time I merge Table1 & Table2 it uses Location & Category 1-4 to bring over a count of matching ID#'s as well as the ID# itself. Then, the next time I only use Location & Category 1-3. Followed by Location & Category 1-2.... etc For a final output that looks like:

Location | Category 1 | Category 2 | Category 3 | Category 4 | Hours | CountMatchingTable2.ID#| Table2.ID#
WAC      | Plane      | Civil      | Recon      | Air        |  1000 | 2                      | 001 (match on Loc & C1-4)
WAC      | Plane      | Civil      | Recon      | Air        |  1000 | 2                      | 002 (match on Loc & C1-4) 
WAC      | Plane      | Military   | Patrol     | Land       |  1000 | 1                      | 003 (match on Loc & C1-3) 
WAC      | Plane      | Civil      |Survey      |Water       |  1000 | 1                      | 004 (match on Loc & C1-2)

Thus far I've created Table2 Grouped by Location & Category 1-4, Table 2 grouped by Location & Category 1-3, Table2 Grouped by Location & Category 1-2, etc... Then, I merge (left outer join) Table1 with Table2 on Location and Category1-4. This duplicates the first record in Table1 and ascribes ID# 001 and ID#002 to the records. The 3rd and 4th Records in Table1 are null because Category 4 and 3 do not match respectively.

Now my problem is I would like to only do the remaining (progressively less detailed) joins on the unmatched records in Table1. However, I can't figure out how to do that exclusively on the unmatched records and when I try to merge Table1 again with Table2 on Location & Category1-3 I duplicate the already matched (1st and 2nd records) from Table1. The end goal here is to divide Hours by the number of matching records in Table2 and then create a relationship back to Table2 using ID#. 

Also if there is a way to do this without having 4 separate queries for Table2 grouped 4 different ways kindly let me know. Thanks in advance.