delete from Likes
where ID1 in (
  select ID1 from (
    select L.ID1, L.ID2
    from Friend F, Likes L
    where F.ID1 = L.ID1
    and F.ID2 = L.ID2
    except
    select L1.ID1, L1.ID2
    from Likes L1, Likes L2
    where L1.ID1 = L2.ID2
    and L1.ID2 = L2.ID1
  )
);