Find all linked records using self join - mysql

Question

I have this table and I am trying to use self join.
I am able to achieve only 50% of the expected results.
create table auto_correct(spell varchar(255), ne varchar(255));
insert into auto_correct values ('test', 'testing');
insert into auto_correct values ('adn', 'and');
insert into auto_correct values ('and', 'andru');
insert into auto_correct values ('testing', 'tested');
insert into auto_correct values ('this', 'that');
insert into auto_correct values ('junk', 'delete');
spell
ne
test
testing
adn
and
and
andru
testing
tested
this
that
junk
delete
The word 'test' is linked to 'tested' through 'testing'
The word 'adn' is linked to 'andru' through 'and'
How do I find all such linked records and display along with non-linked rows?
The expected results are:
spell
ne
test
tested
adn
andru
this
that
junk
delete
I have tried this:
select b.spell, a.ne
from auto_correct as a
left join auto_correct as b on a.spell = b.ne
where b.spell is not null;
returns:
adn
andru
test
tested
The rest of the records where no match is found are missing from above output.

Answer 1

WITH RECURSIVE
cte AS ( SELECT *
FROM auto_correct
WHERE NOT EXISTS ( SELECT NULL
FROM auto_correct ac
WHERE auto_correct.spell = ac.ne )
UNION ALL
SELECT cte.spell, auto_correct.ne
FROM cte
JOIN auto_correct ON cte.ne = auto_correct.spell )
SELECT *
FROM cte
WHERE NOT EXISTS ( SELECT NULL
FROM auto_correct
WHERE auto_correct.spell = cte.ne )
https://dbfiddle.uk/?rdbms=mysql_8.0&fiddle=e90235ce5dde96a7255f8afe1a19d334