Many-to-many relationship to determine if user has liked a post - sql

Question

I have a table that contains all of the posts. I also have a table where a row is added when a user likes a post with foreign keys user_id and post_id.
I want to retrieve a list of ALL of the posts and whether or not a specific user has liked that post. Using an outer join I end up getting some posts twice. Once for user 1 and once for user 2. If I use a WHERE to filter for likes.user_id = 1 AND likes.user_id is NULL I don't get the posts that are only liked by other users.
Ideally I would do this with a single query. SQL isn't my strength, so I'm not even really sure if a sub query is needed or if a join is sufficient.
Apologies for being this vague but I think this is a common enough query that it should make some sense.
EDIT: I have created a DB Fiddle with the two queries that I mentioned. https://www.db-fiddle.com/f/oFM2zWsR9WFKTPJA16U1Tz/4
UPDATE: Figured it out last night. This is what I ended up with:
SELECT
posts.id AS post_id,
posts.title AS post_title,
CASE
WHEN EXISTS (
SELECT *
FROM likes
WHERE posts.id = likes.post_id
AND likes.user_id = 1
) THEN TRUE
ELSE FALSE END
AS liked
FROM posts;
Although I was able to resolve it, thanks to #wildplasser for his answer as well.

Answer 1

Data (I needed to change it a bit, because one should not assign to serials):
CREATE TABLE posts (
id serial,
title varchar
);
CREATE TABLE users (
id serial,
name varchar
);
CREATE TABLE likes (
id serial,
user_id int,
post_id int
);
INSERT INTO posts (title) VALUES ('First Post');
INSERT INTO posts (title) VALUES ('Second Post');
INSERT INTO posts (title) VALUES ('Third Post');
INSERT INTO users (name) VALUES ('Obama');
INSERT INTO users (name) VALUES ('Trump');
INSERT INTO likes (user_id, post_id) VALUES (1, 1);
INSERT INTO likes (user_id, post_id) VALUES (2, 1);
INSERT INTO likes (user_id, post_id) VALUES (2, 2);
-- I want to retrieve a list of ALL of the posts and whether or not a specific user has liked that post
SELECT id, title
, EXISTS(
--EXISTS() yields a boolean value
SELECT *
FROM likes lk
JOIN users u ON u.id = lk.user_id AND lk.post_id=p.id
WHERE u.name ='Obama'
) AS liked_by_Obama
FROM posts p
;
Results:
id | title | liked_by_obama
----+-------------+----------------
1 | First Post | t
2 | Second Post | f
3 | Third Post | f
(3 rows)

Answer 2

As far as I understand, you have two tables such as post table which includes all post from different users and a like table with user.id and post id. if you want to retreive only posts then
select * from posts
if you need user information as well, which is present in user table then you can do below.
select user.user_name, post.postdata from user,post where post.userid=user.userid
in above query, user_name is a column name in user table and postdata is a column in post table.