MySQL 8.0

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create table likes
select 1 user_id, 12 like_user union all
select 12,1 union all
select 1,10 union all
select 5,1;
select * from likes;


user_id
like_user


1
12

12
1

1
10

5
1


SELECT t1.user_id 
FROM likes t1
JOIN likes t2 ON t1.user_id = t2.like_user 
             AND t2.user_id = 1
             AND t1.like_user = 1;


user_id


12