Multi-table recursive SQL

actual result

uid
1
2

answer table

id, source_id, target_id, value
1, 1, 2, a1
2, 2, 3, a2

expected result

uid
1
2
3

query.sql

WITH RECURSIVE questions_with_answers(uid) AS (
	SELECT
	  q.*, a.*
	FROM
	  questions q
	LEFT OUTER JOIN
	  answers a ON (q.id = a.source_id)
	WHERE
	  q.id = 1 -- question start node ID

	UNION ALL

	SELECT
	  q.*, a.*
	FROM
	  questions_with_answers qa
	JOIN
	  questions q ON (qa.target_id = q.id)
	LEFT OUTER JOIN
	  answers a ON (q.id = a.source_id)
)
SELECT uid FROM questions_with_answers WHERE source_id IS NOT NULL AND target_id IS NOT NULL

questions table

id, value
1, q1
2, q2
3, q3