SQL SELECT om cyclische verwijzingen te vinden in de vader-ID-georganiseerde boom?

SELECT  n.*, CONNECT_BY_ROOT(id), level
FROM    elements n
START WITH
        id IN
        (
        SELECT  MIN(id)
        FROM    (
                SELECT  id, CONNECT_BY_ROOT(id) AS root
                FROM    elements
                START WITH
                        id IN
                        (
                        SELECT  id
                        FROM    elements n
                        WHERE   CONNECT_BY_ISCYCLE = 1
                        CONNECT BY NOCYCLE
                                father_id = PRIOR id
                        )
                CONNECT BY NOCYCLE
                        id = PRIOR father_id
                )
        GROUP BY
                root
        )
CONNECT BY NOCYCLE
        id = PRIOR father_id

Misschien wil je dit artikel lezen:

• Lussen in een boom vinden