Hello again,
I will explain as best I can but trying to put together the design of the parts section of my DB and working out what relationships are required. I've simplified it down so that a part can originate from 1 of 2 places, it will either be produced in house at our factory or bought in from an external supplier. Also a part can be bought in from more than 1 supplier depending on price/stock levels. I know this is where the many to many relationships come into play and so far I have done the following:-
Relationship_Parts.pdf
The parts are of course stored in tbl_Parts, a part can have an origin of either in house (made by us) or bought in (externally sourced) so I have added a link table with 2 PK's called tbl_SupplierToPart which links it to the suppliers table, tbl_Suppliers. You will also see another table, tbl_Origin, which I have linked to tbl_Parts but shouldn't this also be a link table between tbl_Parts and tbl_Part_Origin? The reason I ask is because one part doesn't come from just one supplier and a supplier will supply many parts, so is this not a many to many relationship??