Oracle Sql NOT NULL xor NULL? -

i'm selecting group of records , want filter column in logic of xor - not null xor null.

--basic select make, model cars  results -------- ford   taurus ford   (null) toyota camry toyota (null) honda  (null)  --obviously xor not real oracle operator --this i'm trying do.. select make, model cars model not null   xor model null   results (pulls records model not null, falling null if necessary) -------- ford   taurus toyota camry honda  (null) 

can give me insight on how achieve desired result i'm looking for? i'm struggling on one!

many thanks!

select  make, model    (         select  c.*,                 row_number() on (partition make order model nulls last) rn            cars c         )   not (rn > 1 , model null)