I'm not sure if this a bug or if working as intended: the order by b,a seems to cause B to use asc.. Instead of the desc as written in the order by statement.
create table tst (a integer, b integer ); sqlite> insert into tst values(1,1); sqlite> insert into tst values(1,2); sqlite> insert into tst values(1,3); sqlite> insert into tst values(2,3); sqlite> insert into tst values(2,2); sqlite> insert into tst values(2,1); sqlite> select * from tst order by b, a desc; a|b 2|1 1|1 2|2 1|2 2|3 1|3