SELECT m.mountain_range,
p.peak_name,
p.elevation
FROM mountains AS m
INNER JOIN mountains_countries AS mc
ON mc.country_code = 'BG'
AND mc.mountain_id=m.id
LEFT OUTER JOIN peaks AS p
ON p.mountain_id = m.id
WHERE p.id =
(SELECT id FROM peaks
WHERE mountain_id=m.id
ORDER BY elevation DESC LIMIT 1)
OR p.id is null