WITH Q1(ID, NAME)
AS (
VALUES( 1 , '10'), ( 1 , '20'), ( 1 , '30'), ( 3 , '10'), ( 3 , '20'), ( 4 , '11')),

Q2(NUM, ID, NAME)
AS (
SELECT ROW_NUMBER() OVER(PARTITION BY Q1.ID), Q1.ID, Q1.NAME
FROM Q1),

Q3(NUM, ID, NAME)
AS (
SELECT Q2.NUM, Q2.ID, CAST(Q2.NAME AS VARCHAR( 128 ))
FROM Q2
WHERE Q2.NUM =  1 
UNION ALL
SELECT Q2.NUM, Q2.ID, CAST(Q3.NAME || ' ' || Q2.NAME AS VARCHAR( 128 ))
FROM Q2, Q3
WHERE Q2.ID = Q3.ID AND Q2.NUM - Q3.NUM =  1 ),

Q4(ID, NUM)
AS (
SELECT Q3.ID, MAX(Q3.NUM)
FROM Q3
GROUP BY Q3.ID)

SELECT Q3.ID, Q3.NAME
FROM Q3
WHERE EXISTS(SELECT Q4.ID
        FROM Q4
        WHERE Q4.ID = Q3.ID AND Q4.NUM = Q3.NUM)
ORDER BY ID