Id   Name   Other_Columns
-------------------------
1    A       A_data_1
2    A       A_data_2
3    A       A_data_3
4    B       B_data_1
5    B       B_data_2
6    C       C_data_1

1    A       A_data_1
4    B       B_data_1
6    C       C_data_1

3    A       A_data_3
5    B       B_data_2
6    C       C_data_1

select * from (select * from messages ORDER BY id DESC) AS x GROUP BY name

SELECT m1.*
FROM messages m1 LEFT JOIN messages m2
 ON (m1.name = m2.name AND m1.id < m2.id)
WHERE m2.id IS NULL;

SELECT p1.postid
FROM Posts p1
INNER JOIN (SELECT pi.owneruserid, MAX(pi.postid) AS maxpostid
            FROM Posts pi GROUP BY pi.owneruserid) p2
  ON (p1.postid = p2.maxpostid)
WHERE p1.owneruserid = 20860;

1 row in set (1 min 17.89 sec)

+----+-------------+------------+--------+----------------------------+-------------+---------+--------------+---------+-------------+
| id | select_type | table      | type   | possible_keys              | key         | key_len | ref          | rows    | Extra       |
+----+-------------+------------+--------+----------------------------+-------------+---------+--------------+---------+-------------+
|  1 | PRIMARY     | <derived2> | ALL    | NULL                       | NULL        | NULL    | NULL         |   76756 |             |
|  1 | PRIMARY     | p1         | eq_ref | PRIMARY,PostId,OwnerUserId | PRIMARY     | 8       | p2.maxpostid |       1 | Using where |
|  2 | DERIVED     | pi         | index  | NULL                       | OwnerUserId | 8       | NULL         | 1151268 | Using index |
+----+-------------+------------+--------+----------------------------+-------------+---------+--------------+---------+-------------+
3 rows in set (16.09 sec)

SELECT p1.postid
FROM Posts p1 LEFT JOIN posts p2
  ON (p1.owneruserid = p2.owneruserid AND p1.postid < p2.postid)
WHERE p2.postid IS NULL AND p1.owneruserid = 20860;

1 row in set (0.28 sec)

+----+-------------+-------+------+----------------------------+-------------+---------+-------+------+--------------------------------------+
| id | select_type | table | type | possible_keys              | key         | key_len | ref   | rows | Extra                                |
+----+-------------+-------+------+----------------------------+-------------+---------+-------+------+--------------------------------------+
|  1 | SIMPLE      | p1    | ref  | OwnerUserId                | OwnerUserId | 8       | const | 1384 | Using index                          |
|  1 | SIMPLE      | p2    | ref  | PRIMARY,PostId,OwnerUserId | OwnerUserId | 8       | const | 1384 | Using where; Using index; Not exists |
+----+-------------+-------+------+----------------------------+-------------+---------+-------+------+--------------------------------------+
2 rows in set (0.00 sec)

CREATE TABLE `posts` (
  `PostId` bigint(20) unsigned NOT NULL auto_increment,
  `PostTypeId` bigint(20) unsigned NOT NULL,
  `AcceptedAnswerId` bigint(20) unsigned default NULL,
  `ParentId` bigint(20) unsigned default NULL,
  `CreationDate` datetime NOT NULL,
  `Score` int(11) NOT NULL default '0',
  `ViewCount` int(11) NOT NULL default '0',
  `Body` text NOT NULL,
  `OwnerUserId` bigint(20) unsigned NOT NULL,
  `OwnerDisplayName` varchar(40) default NULL,
  `LastEditorUserId` bigint(20) unsigned default NULL,
  `LastEditDate` datetime default NULL,
  `LastActivityDate` datetime default NULL,
  `Title` varchar(250) NOT NULL default '',
  `Tags` varchar(150) NOT NULL default '',
  `AnswerCount` int(11) NOT NULL default '0',
  `CommentCount` int(11) NOT NULL default '0',
  `FavoriteCount` int(11) NOT NULL default '0',
  `ClosedDate` datetime default NULL,
  PRIMARY KEY  (`PostId`),
  UNIQUE KEY `PostId` (`PostId`),
  KEY `PostTypeId` (`PostTypeId`),
  KEY `AcceptedAnswerId` (`AcceptedAnswerId`),
  KEY `OwnerUserId` (`OwnerUserId`),
  KEY `LastEditorUserId` (`LastEditorUserId`),
  KEY `ParentId` (`ParentId`),
  CONSTRAINT `posts_ibfk_1` FOREIGN KEY (`PostTypeId`) REFERENCES `posttypes` (`PostTypeId`)
) ENGINE=InnoDB;

SELECT test_id, MAX(request_id), request_id
FROM testresults
GROUP BY test_id DESC;

SELECT test_id, request_id
FROM (
    SELECT test_id, MAX(request_id), request_id
    FROM testresults
    GROUP BY test_id DESC) as ids
    ORDER BY test_id;

SELECT test_id, request_id
FROM testresults, (SELECT @group:=NULL) as init
WHERE IF(IFNULL(@group, -1)=@group:=test_id, 0, 1)
ORDER BY test_id DESC, request_id DESC

select
    a.*
from
    messages a
    inner join
        (select name, max(id) as maxid from messages group by name) as b on
        a.id = b.maxid

select
    a.*
from
    messages a
    inner join
        (select name, max(other_col) as other_col
         from messages group by name) as b on
        a.name = b.name
        and a.other_col = b.other_col

WITH Ranked AS (
  SELECT Id, Name, OtherColumns,
    ROW_NUMBER() OVER (
      PARTITION BY Name
      ORDER BY Id DESC
    ) AS rk
  FROM messages
)
  SELECT Id, Name, OtherColumns
  FROM messages
  WHERE rk = 1;

SELECT
  Id, Name, OtherColumns
FROM messages
WHERE NOT EXISTS (
  SELECT * FROM messages as M2
  WHERE M2.Name = messages.Name
  AND M2.Id > messages.Id
)

select * from messages where id in
(select max(id) from messages group by Name)

select m1.* from messages m1
left outer join messages m2
on ( m1.id<m2.id and m1.name=m2.name )
where m2.id is null

SELECT jos_categories.title AS name,
       joined .catid,
       joined .title,
       joined .introtext
FROM   jos_categories
       INNER JOIN (SELECT *
                   FROM   (SELECT `title`,
                                  catid,
                                  `created`,
                                  introtext
                           FROM   `jos_content`
                           WHERE  `sectionid` = 6
                           ORDER  BY `id` DESC) AS yes
                   GROUP  BY `yes`.`catid` DESC
                   ORDER  BY `yes`.`created` DESC) AS joined
         ON( joined.catid = jos_categories.id )

SELECT *, Max(Id) FROM messages GROUP BY Name

SELECT M1.*
FROM MESSAGES M1,
(
 SELECT SUBSTR(Others_data,1,2),MAX(Others_data) AS Max_Others_data
 FROM MESSAGES
 GROUP BY 1
) M2
WHERE M1.Others_data = M2.Max_Others_data
ORDER BY Others_data;

SELECT id, name, other_columns
FROM messages
WHERE id IN (
    SELECT MAX(id)
    FROM messages
    GROUP BY name
);

DELETE FROM messages WHERE id NOT IN
 (SELECT m1.id
 FROM messages m1 LEFT JOIN messages m2
 ON (m1.name = m2.name AND m1.id < m2.id)
 WHERE m2.id IS NULL)

DROP TABLE IF EXISTS UniqueIDs;
CREATE Temporary table UniqueIDs (id Int(11));

INSERT INTO UniqueIDs
    (SELECT T1.ID FROM Table T1 LEFT JOIN Table T2 ON
    (T1.Field1 = T2.Field1 AND T1.Field2 = T2.Field2 #Comparison Fields
    AND T1.ID < T2.ID)
    WHERE T2.ID IS NULL);

DELETE FROM Table WHERE id NOT IN (SELECT ID FROM UniqueIDs);

SELECT
  `Id`,
  `Name`,
  SUBSTRING_INDEX(
    GROUP_CONCAT(
      `Other_Columns`
      ORDER BY `Id` DESC
      SEPARATOR '||'
    ),
    '||',
    1
  ) Other_Columns
FROM
  messages
GROUP BY `Name`