SELECT country_name, 
       count( country_name ) AS num_of_neighbours , 
       sum( border_length ) AS sum_of_border_length
FROM neighbours, country
WHERE country_name = country1
   OR country_name = country2
GROUP BY country_name
UNION 
SELECT country_name,0,0 
FROM neighbours , country
WHERE country_name NOT in ( 
   SELECT country1 as country_name FROM neighbours  
    UNION
   SELECT country2 as country_name FROM neighbours)