MySQL 8.0

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CREATE TABLE conversations
    (`iD` int, `From` int, `to` int, `Message` varchar(5), `Read` int, `Created_at` varchar(19))
;
INSERT INTO conversations
    (`iD`, `From`, `to`, `Message`, `Read`, `Created_at`)
VALUES
    (1, 2, 1, 'blah1', 0, '2019-01-11 02:15:24'),
    (2, 1, 2, 'blah2', 0, '2019-01-11 02:16:24'),
    (3, 2, 1, 'blah3', 0, '2019-01-11 02:17:24'),
    (4, 2, 3, 'blah4', 0, '2019-01-11 02:18:24'),
    (5, 1, 5, 'blah5', 0, '2019-01-11 02:19:24'),
    (6, 1, 3, 'blah6', 0, '2019-01-11 02:20:24')

Records: 6  Duplicates: 0  Warnings: 0


SELECT CASE WHEN `From` = 1 THEN `To` ELSE `From` END AS other, MAX(Created_at) AS latest
FROM conversations
WHERE `From` = 1 OR `To` = 1
GROUP BY other


other
latest


2
2019-01-11 02:17:24

5
2019-01-11 02:19:24

3
2019-01-11 02:20:24


SELECT c.*
FROM conversations c
JOIN (SELECT CASE WHEN `From` = 1 THEN `To` ELSE `From` END AS other, MAX(Created_at) AS latest
      FROM conversations
      WHERE `From` = 1 OR `To` = 1
      GROUP BY other) m
  ON (c.From = 1 AND c.To = m.other OR c.To = 1 AND c.From = m.other) AND c.Created_at = m.latest


iD
From
to
Message
Read
Created_at


3
2
1
blah3
0
2019-01-11 02:17:24

5
1
5
blah5
0
2019-01-11 02:19:24

6
1
3
blah6
0
2019-01-11 02:20:24

other	latest
2	2019-01-11 02:17:24
5	2019-01-11 02:19:24
3	2019-01-11 02:20:24

iD	From	to	Message	Created_at
3	2	1	blah3	2019-01-11 02:17:24
5	1	5	blah5	2019-01-11 02:19:24
6	1	3	blah6	2019-01-11 02:20:24