WITH skill_groups AS (
	SELECT DISTINCT group_id FROM skill_data
)
SELECT
	g.group_id,
	COALESCE(inh_from.id, s1.id, 0) AS skill1,
	COALESCE(inh_to.id, s2.id, 0) AS skill2,
	IFNULL(s3.id, 0) AS skill3,
	IFNULL(m1.id, 0) AS skill_bad
FROM skill_groups g
	LEFT JOIN skill_data s1 ON g.group_id = s1.group_id AND s1.group_rate = 1
	LEFT JOIN skill_data s2 ON g.group_id = s2.group_id AND s2.group_rate = 2
	LEFT JOIN skill_data s3 ON g.group_id = s3.group_id AND s3.group_rate = 3
	LEFT JOIN skill_data m1 ON g.group_id = m1.group_id AND m1.group_rate = -1
	LEFT JOIN skill_data inh_to ON s1.id = inh_to.unique_skill_id_1
	LEFT JOIN skill_data inh_from ON s2.unique_skill_id_1 = inh_from.id
ORDER BY g.group_id