The first recursive view definition demonstrates a correct use of a right outer join, which is bold. The usage is valid because the recursive relation in the recursive statement of the view definition is used as the outer relation in the right outer join.
CREATE RECURSIVE VIEW rec (f1, mycount) AS (
SELECT a1, 0 AS mycount
FROM nonrec
UNION ALL
SELECT a2, mycount + 1
FROM nonrec RIGHT OUTER JOIN rec ON nonrec.a1 = rec.f1
WHERE rec.mycount <= 100);
The second recursive view definition demonstrates a non-valid use of a right outer join, which is bold. The usage is not valid because the recursive relation in the recursive statement of the view definition is used as the inner relation in the right outer join.
CREATE RECURSIVE VIEW rec (f1, mycount) AS (
SELECT a1, 0 AS mycount
FROM nonrec
UNION ALL
SELECT a2, mycount + 1
FROM rec RIGHT OUTER JOIN nonrec ON nonrec.a1 = rec.f1
WHERE rec.mycount <= 100);
Right outer joins can be used without restriction in the seed statement of a recursive view definition.