recursive from old to latest new with recursive cycle, Oracle

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--Oracle 11g Express Edition
--please drop objects you've created at the end of the script 
--or check for their existance before creating
--'\\' is a delimiter

create table mytable (old varchar2(10), new varchar2(10))\\
insert into mytable (old, new) values ('a','b')\\
insert into mytable (old, new) values ('b','c')\\
insert into mytable (old, new) values ('d','e')\\
---- creating a cycle
insert into mytable (old, new) values ('e','a')\\

insert into mytable (old, new) values ('aa','bb')\\
insert into mytable (old, new) values ('bb','ff')\\

insert into mytable (old, new) values ('11','33')\\
insert into mytable (old, new) values ('33','523')\\
insert into mytable (old, new) values ('523','4444')\\
---- creating another cycle
insert into mytable (old, new) values ('4444','33')\\

with cte(old, new, lev) as
(
	select old, new, 1 as lev from mytable
	union all
	select m.old, cte.new, cte.lev + 1
	from mytable m
	join cte on cte.old = m.new
    where cte.lev < 6 --- trying to break the cycle
)
select old, max(new) keep (dense_rank last order by lev)
from cte
group by old
order by old\\

drop table mytable\\


Absolute service time: 0,9 sec, absolute service time: 0,89 sec