Е, не мога да кажа нищо за ORACLE, но можете да го управлявате с рекурсивен CTE в sql сървър. Ето моето примерно решение, то прави това, което поискахте, ако приемем, че имате таблица, която картографира връзката много към много от една таблица към себе си
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