-- create view
create view all_border_pairs as
select Country1, Country2 from borders
union all
select Country2, Country1 from borders;

-- query
select distinct b1.Country1, b2.Country2
from all_border_pairs b2
join all_border_pairs b1 on b2.Country1 = b1.Country2
where b2.Country2 <> b1.Country1
  and b1.Country1 = 'I' -- optionally filter for one country here
  and not b2.country2 in (select Country2 from all_border_pairs where Country1 = b1.Country1)
order by b1.Country1;