[AccessD] A momentary lapse of reason

Good morning all
Please forgive the title but Pink Floyd's cd is in front of me and I  
thought the title quite apt to my mental processes this morning.  But...  
 
 
I have problem: I have 2 tables. One holds Parts Rejected and the  other 
holds Parts Received. Each table has 2 common fields, SupplierID and AP  
(Accounting Period).  In  PartsRejects table I have total parts rejected by 
supplierID and AP. In  PartsReceived I have total parts received by supplierID 
and AP.  
When I run a query linking these tables have missing rows in both. While  
this many appear to be the classical relationship of  many-to-many, but is 
it?  The PartsReceived table is imported to  Access once each accounting 
period from accounts software.  
A question!  I need a query to show All rows from both  tabels, however 
when I use either a Left Join or Inner Join I get all rows from  the left sided 
table but loose rows from the right side where there is no match  or rows 
are absent on the Left sided table.   
Creating a Link or Junction table causes problems because I have to  
populate this table each accounting period. 
Anyone done this type of thing before? 
TIA 
johnc