SQL - Koppelingen maken tussen velden (transitieve relatie)

Nou, ik kan niets zeggen voor ORACLE, maar je zou het kunnen beheren met recursieve CTE in sql-server. Hier is mijn voorbeeldoplossing, het doet wat je vroeg, ervan uitgaande dat je een tabel hebt die de relatie veel-op-veel van de ene tabel naar zichzelf toewijst

DECLARE @testData table (EntityID int, EntityName varchar(1))
DECLARE @EntityRelations table (EntityID1 int, EntityID2 int)

INSERT INTO @testData
SELECT 1, 'A'
UNION
SELECT 2, 'B'
UNION
SELECT 3, 'C'
UNION
SELECT 4, 'D'
UNION
SELECT 5, 'E'
UNION
SELECT 6, 'F'
UNION
SELECT 7, 'G'
UNION
SELECT 8, 'Y'
UNION
SELECT 9, 'Z'

INSERT INTO @EntityRelations
SELECT 1, 2
UNION
SELECT 9, 2
UNION
SELECT 8, 2
UNION
SELECT 2, 3
UNION
SELECT 2, 4
UNION
SELECT 4, 5
UNION
SELECT 6, 7;


WITH Affiliations (EntityID, Entity1Name, Entity2Name) AS
(
    SELECT r.EntityID1
          ,e.EntityName as Entity1Name
          ,e2.EntityName as Entity2Name
    FROM @EntityRelations r
        JOIN @testData e ON e.EntityID = r.EntityID1
        JOIN @testData e2 ON e2.EntityID = r.EntityID2

    UNION ALL

    SELECT r.EntityID1
          ,e.EntityName as Entity1Name
          ,e2.EntityName as Entity2Name
    FROM @EntityRelations r
        JOIN @testData e ON e.EntityID = r.EntityID1
        JOIN @testData e2 ON e2.EntityID = r.EntityID2
        JOIN Affiliations a ON a.EntityID = r.EntityID2
)

,AffiliationsReverse (EntityID, Entity1Name, Entity2Name) AS
(
    SELECT r.EntityID2
          ,e.EntityName as Entity1Name
          ,e2.EntityName as Entity2Name
    FROM @EntityRelations r
        JOIN @testData e ON e.EntityID = r.EntityID1
        JOIN @testData e2 ON e2.EntityID = r.EntityID2

    UNION ALL

    SELECT r.EntityID2
          ,e.EntityName as Entity1Name
          ,e2.EntityName as Entity2Name
    FROM @EntityRelations r
        JOIN @testData e ON e.EntityID = r.EntityID1
        JOIN @testData e2 ON e2.EntityID = r.EntityID2
        JOIN AffiliationsReverse a ON a.EntityID = r.EntityID1
)


SELECT DISTINCT EntityName
FROM
(
SELECT a.Entity1Name AS EntityName
FROM Affiliations a
    JOIN AffiliationsReverse ar ON ar.EntityID = a.EntityID

UNION

SELECT a.Entity2Name AS EntityName
FROM Affiliations a
    JOIN AffiliationsReverse ar ON ar.EntityID = a.EntityID

UNION

SELECT ar.Entity1Name AS EntityName
FROM Affiliations a
    JOIN AffiliationsReverse ar ON ar.EntityID = a.EntityID

UNION

SELECT ar.Entity2Name AS EntityName
FROM Affiliations a
    JOIN AffiliationsReverse ar ON ar.EntityID = a.EntityID


) s