Get the newest record from each group - mysql

Question

I want to sort the last messages with every user that a specific user has chated from ejabberd archive table.
The fields that I'm using are these
id (message id)
username (username copy)
bare_peer (user that is chatting with)
txt (text chat)
created_at (time created)
What I'm trying to achieve is something like that, but I need to group message by bare_peer with username as 1_usernode, but only the last messages.
I already tested a lot of queries, but none of them worked.
This is the first query I tried.
SELECT id, username, bare_peer, txt FROM archive where
username = '1_usernode' GROUP BY bare_peer ORDER BY created_at DESC;
And this is the output.
+------+------------+-------------------------------------------------------+---------------------+
| id | username | bare_peer | txt | created_at |
+------+------------+------------------------+------------------------------+---------------------+
| 1095 | 1_usernode | 10_usernode#localhost | Hello !!! | 2016-07-17 21:15:17 |
| 1034 | 1_usernode | 15_usernode#localhost | hey sup ? | 2016-07-13 22:40:29 |
| 1107 | 1_usernode | 13_usernode#localhost | oi | 2016-07-18 00:09:28 |
| 1078 | 1_usernode | 2_usernode#localhost | Hello this is just a Test!!! | 2016-07-15 16:30:50 |
| 1101 | 1_usernode | 7_usernode#localhost | hey | 2016-07-18 00:05:55 |
| 1084 | 1_usernode | 3_usernode#localhost | Hey how are you? | 2016-07-15 19:36:44 |
| 1085 | 1_usernode | 4_usernode#localhost | Hey how are you doing ? | 2016-07-17 19:20:00 |

Answer 1

Use This Query It's Helful.
SELECT MAX(id), username, bare_peer, txt FROM archive where
username = '1_usernode' ORDER BY created_at DESC

Answer 2

declare created_at as datetime
try this
DROP TABLE IF EXISTS `archive`;
CREATE TABLE `archive` (
`id` INT(11) NOT NULL AUTO_INCREMENT,
`username` VARCHAR(50) DEFAULT NULL,
`bare_peer` VARCHAR(50) DEFAULT NULL,
`txt` TEXT,
`created_at` DATETIME DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=INNODB DEFAULT CHARSET=latin1;
/*Data for the table archive */
INSERT INTO `archive`(`id`,`username`,`bare_peer`,`txt`,`created_at`)
VALUES (1034,'1_usernode','15_usernode#localhost','hey sup ?','2016-07-13 22:40:29'),
(1078,'1_usernode','2_usernode#localhost','Hello this IS just a Test!!!','2016-07-15 16:30:50'),
(1084,'1_usernode','3_usernode#localhost','Hey how are you?','2016-07-15 19:36:44'),
(1085,'1_usernode','4_usernode#localhost','Hey how are you doing ?','2016-07-17 19:20:00'),
(1095,'1_usernode','10_usernode#localhost','Hello !!!','2016-07-17 21:15:17'),
(1101,'1_usernode','7_usernode#localhost','hey','2016-07-18 00:05:55'),
(1107,'1_usernode','13_usernode#localhost','oi','2016-07-18 00:09:28');
Then run your query
SELECT id, username, bare_peer, txt FROM archive where
username = '1_usernode' GROUP BY bare_peer ORDER BY created_at DESC;

Answer 3

Try this query :-
SELECT archive.id, archive.max_id, archive.username, archive.bare_peer, archive.txt
FROM archive join
(SELECT MAX(id) max_id, username, bare_peer, txt
FROM archivewhere username = '1_usernode' GROUP BY bare_peer)
tab on archive.id=tab.max_id

Answer 4

Try this following code:-
select m.*
from
messages m
inner join (
select max(id) as maxid
from messages
group By (if(username > bare_peer, username, bare_peer)),
(if(username > bare_peer, bare_peer, username))
) t1 on m.id=t1.maxid ;
m is alias of message table

Answer 5

You want the entry with max(created_at) for every username and bare_peer.
One way to do that in MySQL is with 'having' but I don't like that.
I would first get the max(created_at) for every entry:
select username, bare_peer, max(created_at) as m_
from archive
group by username, bare_peer;
Then join the table on that result:
select b.*
from (
select username, bare_peer, max(created_at) as m_
from archive
group by username, bare_peer
) a
inner join archive as b on (
a.username = b.username
and a.bare_peer = b.bare_peer
and a.m_ = b.created_at
)

Answer 6

I want to know why it shows the created_at column when you don't select created_at? And I don't know why you use group by? There is nothing need to be divided into groups.
My statement looks like this.select id, username, bare_peer, txt, created_at from archive where username = '1_usercode' order by created_at desc

Answer 7

I created a temporary solution with the Rahauto's answer.
I put his query that returns me the correct id from latest message inside a
subquery so that i can extract message content from it's id.
SELECT username, bare_peer, txt, created_at FROM archive WHERE id IN (
SELECT tab.max_id FROM
archive JOIN (SELECT MAX(id) max_id, username, bare_peer, txt FROM
archive WHERE username = '1_usernode' GROUP BY bare_peer)
tab ON archive.id=tab.max_id
);