Find all linked records using self join

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