I've read and experienced that when DL/NW has a flight with a single number that if you are flying from city A to C, you only get that mileage, even if en route the flight stops in city B.

But what if I ticket (as one ticket), the flight A to B on Delta then B to C on Northwest (assuming its actually the same flight - Orbitz seems able to do this, say for example SEA-NRT-HKG )? Would I get the full mileage, or do I still only get the SEA-HKG mileage? I've done a search for threads about this, but have yet to find input on how this plays out.