Oracle 18c

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create table t (
  abflug varchar2(10),
  ankunft varchar2(10)
);
insert into t (abflug, ankunft) values ('Wien', 'Pressburg');
1 rows affected

insert into t (abflug, ankunft) values ('Wien', 'Laibach');
1 rows affected

insert into t (abflug, ankunft) values ('Laibach', 'Paris');
1 rows affected

insert into t (abflug, ankunft) values ('Laibach', 'Belgrad');
1 rows affected

insert into t (abflug, ankunft) values ('Belgrad', 'Athen');
1 rows affected

insert into t (abflug, ankunft) values ('Athen', 'Wien');
1 rows affected

with
c (abflug, ankunft, lvl) as (
  select abflug, ankunft, 1 from t where abflug = 'Wien'
  union all
  select t.abflug, t.ankunft, c.lvl + 1
  from c
  join t on t.abflug = c.ankunft and c.lvl <= 4
)
select * from c;


ABFLUG
ANKUNFT
LVL


Wien
Pressburg
1

Wien
Laibach
1

Laibach
Paris
2

Laibach
Belgrad
2

Belgrad
Athen
3

Athen
Wien
4

Wien
Pressburg
5

Wien
Laibach
5

ABFLUG	ANKUNFT	LVL
Wien	Pressburg	1
Wien	Laibach	1
Laibach	Paris	2
Laibach	Belgrad	2
Belgrad	Athen	3
Athen	Wien	4
Wien	Pressburg	5
Wien	Laibach	5