Postgres 13

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create table memorization_word_translation
(
    id           serial  not null,
    from_word_id integer not null,
    to_word_id   integer not null
);

insert into memorization_word_translation (from_word_id, to_word_id) values
(35,36),
(35,37),
(36,35),
(37,35),
(37,39),
(39,37);

SELECT * FROM memorization_word_translation
6 rows affected



id
from_word_id
to_word_id


1
35
36

2
35
37

3
36
35

4
37
35

5
37
39

6
39
37


-- yours
select * from memorization_word_translation
where from_word_id = 35 or to_word_id = 35


id
from_word_id
to_word_id


1
35
36

2
35
37

3
36
35

4
37
35


select distinct on (
    CASE 
        WHEN (from_word_id >= to_word_id) THEN (from_word_id, to_word_id)
        ELSE (to_word_id, from_word_id)
    END 
)
    * 
from memorization_word_translation
where from_word_id = 35 or to_word_id = 35


id
from_word_id
to_word_id


1
35
36

2
35
37