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WITH
minComp
AS
(
	SELECT MIN(ID_comp) AS ID_comp
	FROM Trip
),
maxComp
AS
(
	SELECT MAX(ID_comp) AS ID_comp
	FROM Trip
),
genUp
AS
(
	SELECT
	(
		SELECT ID_comp
		FROM minComp
	) AS ID_comp
	UNION ALL
	SELECT ID_comp + 1 AS ID_comp
	FROM genUp
	WHERE ID_comp + 1 <=
	(
		SELECT ID_comp
		FROM maxComp
	)
),
compAndHill
AS
(
	SELECT DISTINCT lt.ID_comp, rt.ID_comp AS hill
	FROM trip lt
	CROSS JOIN genUp rt
),
corectCompAndHill
AS
(
	SELECT ID_comp, hill
	FROM compAndHill
	WHERE hill <= ID_comp
),
corectCompAndHillNoEql
AS
(
	SELECT ID_comp, hill
	FROM compAndHill
	WHERE hill < ID_comp
),
compTwoHills
AS
(
	SELECT lt.ID_comp, STRING_AGG(lt.hill,'') WITHIN GROUP(ORDER BY lt.ID_comp) AS hill1, STRING_AGG(REVERSE(rt.hill),'') WITHIN GROUP(ORDER BY lt.ID_comp) AS hill2
	FROM corectCompAndHill lt
	LEFT JOIN corectCompAndHillNoEql rt ON lt.ID_comp = rt.ID_comp AND lt.hill = rt.hill
	GROUP BY lt.ID_comp
)
SELECT ID_comp, CONCAT(hill1, REVERSE(hill2)) AS hill
FROM compTwoHills