MySQL 8.0

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select version();


version()


8.0.18


CREATE TABLE `db_user` (
  `db_user_id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `name` varchar(255) NOT NULL,
  `balance` decimal(10,2) NOT NULL,
  PRIMARY KEY (`db_user_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 AUTO_INCREMENT=1;
CREATE TABLE `db_comment` (
  `db_comment_id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `db_user_id` int(10) unsigned NOT NULL,
  `text` text NOT NULL,
  PRIMARY KEY (`db_comment_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 AUTO_INCREMENT=1;
INSERT INTO db_user(db_user_id, name, balance)
VALUES ('1','Ivan', '100'),
       ('2','Petr', '154'),
       ('3','Artur', '430'),
       ('4','John', '25');
INSERT INTO db_comment(db_comment_id, db_user_id, text)
VALUES ('1','1', 'Message1 ivan'),
       ('2','1', 'Message2 ivan'),
       ('3','2', 'Message1 petr'),
       ('4','2', "Message2 petr"),
       ('5','1', 'Message3 ivan'),
       ('6','4', 'Message1 john'),
       ('7','3', 'Message1 artur'),
       ('8','2', 'Message3 Petr'),
       ('9','3', "Message2 Artur"),
       ('10','4', 'Message2 John');
SELECT
  u.name,
  c.text
FROM db_user u
JOIN db_comment c ON c.db_user_id = u.db_user_id
                  AND NOT EXISTS
                  (
                    SELECT *
                    FROM db_comment c2
                    WHERE c2.db_user_id = c.db_user_id
                    AND c2.db_comment_id > c.db_comment_id
                  );


name
text


Ivan
Message3 ivan

Petr
Message3 Petr

Artur
Message2 Artur

John
Message2 John


SELECT
  u.name,
  c.text
FROM db_user u
JOIN db_comment c ON c.db_user_id = u.db_user_id
                  AND (c.db_user_id, c.db_comment_id) IN
                  (
                    SELECT db_user_id, MAX(db_comment_id)
                    FROM db_comment
                    GROUP BY db_user_id
                  );


name
text


Ivan
Message3 ivan

Petr
Message3 Petr

Artur
Message2 Artur

John
Message2 John


SELECT
  u.name,
  c.text
FROM db_user u
JOIN 
(
  SELECT
    db_user_id,
    text,
    ROW_NUMBER() OVER (PARTITION BY db_user_id ORDER BY db_comment_id DESC) AS rn
  FROM db_comment
) c ON c.db_user_id = u.db_user_id AND c.rn = 1;


name
text


Ivan
Message3 ivan

Petr
Message3 Petr

Artur
Message2 Artur

John
Message2 John
name	text
Ivan	Message3 ivan
Petr	Message3 Petr
Artur	Message2 Artur
John	Message2 John