Oracle 18c

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CREATE TABLE t ( parent, child ) AS
  SELECT 'a', 'b' FROM dual UNION ALL
  SELECT 'b', 'c' FROM dual UNION ALL
  SELECT 'c', 'd' FROM dual UNION ALL
  SELECT 'd', 'e' FROM dual;
4 rows affected

SELECT level,
       t.*
FROM   t
START WITH parent = 'b'
CONNECT BY PRIOR child = parent


LEVEL
PARENT
CHILD


1
b
c

2
c
d

3
d
e


SELECT level,
       t.*,
       SYS_CONNECT_BY_PATH( '('||col1||','||col2||')', '->' ) AS path
FROM (
  SELECT 'a' AS col1, 'b' AS col2 FROM dual UNION ALL
  SELECT 'c', 'd' FROM dual
) t
CONNECT BY level <= 3


LEVEL
COL1
COL2
PATH


1
a
b
->(a,b)

2
a
b
->(a,b)->(a,b)

3
a
b
->(a,b)->(a,b)->(a,b)

3
c
d
->(a,b)->(a,b)->(c,d)

2
c
d
->(a,b)->(c,d)

3
a
b
->(a,b)->(c,d)->(a,b)

3
c
d
->(a,b)->(c,d)->(c,d)

1
c
d
->(c,d)

2
a
b
->(c,d)->(a,b)

3
a
b
->(c,d)->(a,b)->(a,b)

3
c
d
->(c,d)->(a,b)->(c,d)

2
c
d
->(c,d)->(c,d)

3
a
b
->(c,d)->(c,d)->(a,b)

3
c
d
->(c,d)->(c,d)->(c,d)

LEVEL	COL1	COL2	PATH
1	a	b	->(a,b)
2	a	b	->(a,b)->(a,b)
3	a	b	->(a,b)->(a,b)->(a,b)
3	c	d	->(a,b)->(a,b)->(c,d)
2	c	d	->(a,b)->(c,d)
3	a	b	->(a,b)->(c,d)->(a,b)
3	c	d	->(a,b)->(c,d)->(c,d)
1	c	d	->(c,d)
2	a	b	->(c,d)->(a,b)
3	a	b	->(c,d)->(a,b)->(a,b)
3	c	d	->(c,d)->(a,b)->(c,d)
2	c	d	->(c,d)->(c,d)
3	a	b	->(c,d)->(c,d)->(a,b)
3	c	d	->(c,d)->(c,d)->(c,d)