MySQL 5.7

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CREATE TABLE post
    (`id` int, `title` varchar(6))
;
    
INSERT INTO post
    (`id`, `title`)
VALUES
    (0, 'titleA'),
    (1, 'titleB'),
    (2, 'titleC')
;


CREATE TABLE comment
    (`id` int, `id_post` int, `text` varchar(40))
;
    
INSERT INTO comment
    (`id`, `id_post`, `text`)
VALUES
    (1, 0, 'blaa'),
    (2, 0, 'blbb'),
    (3, 1, 'aaaa'),
    (4, 1, 'bbbb') 
;



CREATE TABLE comment_likes
    (`id` int auto_increment primary key, `id_comment` int, `vote` int)
;
    
INSERT INTO comment_likes
    (`id_comment`, `vote`)
VALUES
    (1, +1),
    (1, +1),
    (1, +1),
    (1, +1),
    (1, +1),
    (1, -1),
    (1, +1),
    (2, +7), -- cheat for adding 7 rows
    (3, +5), -- cheat for adding 10 rows
    (3, +5),
    (4, +1),
    (4, +1),
    (4, +1)
;
SELECT * FROM post;
SELECT * FROM comment;
SELECT * FROM comment_likes


id
title


0
titleA

1
titleB

2
titleC




id
id_post
text


1
0
blaa

2
0
blbb

3
1
aaaa

4
1
bbbb




id
id_comment
vote


1
1
1

2
1
1

3
1
1

4
1
1

5
1
1

6
1
-1

7
1
1

8
2
7

9
3
5

10
3
5

11
4
1

12
4
1

13
4
1


-- SET @@sql_mode = 'STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION';
SELECT   p.id AS post_id
         , ( SELECT  c.id AS comment_id
              FROM   comment c INNER JOIN comment_likes l ON l.id_comment = c.id
              WHERE  c.id_post = p.id
              GROUP BY c.id
              ORDER BY SUM(vote) DESC
              LIMIT 1
          ) AS comment_id
          , ( SELECT SUM(l.vote) 
              FROM   comment c INNER JOIN comment_likes l ON l.id_comment = c.id
              WHERE  p.id = c.id_post
              GROUP BY c.id
              ORDER BY SUM(l.vote) DESC
              LIMIT 1
          ) AS total_like_votes
FROM   post p 
HAVING total_like_votes IS NOT NULL


post_id
comment_id
total_like_votes


0
2
7

1
3
10