show create table users \G EXPLAIN select a.* from users as a, hands as b where a.id = b.user_id group by b.user_id order by a.created_at desc;
*************************** 1. row ***************************
       Table: users
Create Table: CREATE TABLE `users` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `login` varchar(50) DEFAULT NULL,
  `email` varchar(50) DEFAULT NULL,
  `api_key` varchar(50) DEFAULT NULL,
  `facebook_uid` decimal(10,0) DEFAULT NULL,
  `myspace_uid` decimal(10,0) DEFAULT NULL,
  `admin` tinyint(4) DEFAULT '0',
  `avatar` varchar(50) DEFAULT 'default.jpg',
  `onlinetime` datetime DEFAULT NULL,
  `password_reset_key` varchar(50) DEFAULT NULL,
  `activated_at` datetime DEFAULT NULL,
  `activation_code` varchar(50) DEFAULT NULL,
  `bigbets` int(11) DEFAULT '200',
  `reloadint` int(11) DEFAULT '10000',
  `crypted_password` varchar(50) DEFAULT NULL,
  `salt` varchar(50) DEFAULT NULL,
  `twittoken` varchar(50) DEFAULT NULL,
  `twitsecret` varchar(50) DEFAULT NULL,
  `created_at` datetime DEFAULT NULL,
  `public` tinyint(4) DEFAULT NULL,
  `staked` tinyint(4) DEFAULT NULL,
  `shared_key` varchar(50) DEFAULT NULL,
  `mailings` tinyint(4) DEFAULT '1',
  `moderator` tinyint(4) DEFAULT '0',
  `viewed_alert` tinyint(4) DEFAULT '0',
  `epw` varchar(50) DEFAULT NULL,
  `mid` int(11) DEFAULT NULL,
  `banned` tinyint(1) DEFAULT '0',
  `processed` tinyint(1) DEFAULT '0',
  `reminded` tinyint(1) DEFAULT '0',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=950 DEFAULT CHARSET=utf8
1 row in set (0.00 sec)

+----+-------------+-------+--------+---------------+---------+---------+--------------------------------+--------+----------------------------------------------+
| id | select_type | table | type   | possible_keys | key     | key_len | ref                            | rows   | Extra                                        |
+----+-------------+-------+--------+---------------+---------+---------+--------------------------------+--------+----------------------------------------------+
|  1 | SIMPLE      | b     | index  | user_id       | user_id | 5       | NULL                           | 789554 | Using index; Using temporary; Using filesort |
|  1 | SIMPLE      | a     | eq_ref | PRIMARY       | PRIMARY | 4       | bluffware_production.b.user_id |      1 |                                              |
+----+-------------+-------+--------+---------------+---------+---------+--------------------------------+--------+----------------------------------------------+
2 rows in set (0.01 sec)


mysql> show create table hands \G;
*************************** 1. row ***************************
       Table: hands
Create Table: CREATE TABLE `hands` (
  `id` varchar(11) NOT NULL,
  `number` varchar(50) DEFAULT NULL,
  `is_public` tinyint(4) DEFAULT '0',
  `site_id` int(11) DEFAULT NULL,
  `tablename` char(50) DEFAULT NULL,
  `user_id` int(11) DEFAULT NULL,
  `small` int(11) DEFAULT NULL,
  `big` int(11) DEFAULT NULL,
  `ante` int(11) DEFAULT NULL,
  `game` varchar(50) DEFAULT NULL,
  `structure` varchar(50) DEFAULT NULL,
  `played_at` datetime DEFAULT NULL,
  `cards` varchar(50) DEFAULT '',
  `session` tinyint(4) DEFAULT NULL,
  `fkey` int(11) DEFAULT NULL,
  `net` int(11) DEFAULT '0',
  `visible` tinyint(4) DEFAULT '1',
  `viewed` int(11) DEFAULT '0',
  `batch_id` varchar(50) DEFAULT NULL,
  `created_at` datetime DEFAULT NULL,
  `potsize` int(11) DEFAULT '0',
  `winner` varchar(50) DEFAULT NULL,
  `sng` tinyint(4) DEFAULT '0',
  `scribed` tinyint(4) DEFAULT '0',
  `index_id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  PRIMARY KEY (`index_id`),
  KEY `id` (`id`),
  KEY `user_id` (`user_id`)
) ENGINE=InnoDB AUTO_INCREMENT=801642 DEFAULT CHARSET=utf8
1 row in set (0.13 sec)

ERROR:
No query specified