mysql merge table

SELECT COUNT(*) FROM `comment` 

SHOW CREATE TABLE `comment`

CREATE TABLE `comment1` (
  `id` INT(8) NOT NULL AUTO_INCREMENT,
  `blogUser` VARCHAR(20) NOT NULL,
  `replayUser` VARCHAR(20) NOT NULL,
  `articleId` INT(8) NOT NULL DEFAULT '0',
  `content` TEXT,
  `addTime` DATETIME NOT NULL,
  PRIMARY KEY (`id`),
  KEY `addTime` (`addTime`),
  KEY `replayUser` (`replayUser`)
) ENGINE=MYISAM AUTO_INCREMENT=1000004 DEFAULT CHARSET=utf8
INSERT INTO comment1 SELECT  `id` ,
  `blogUser`,
  `replayUser`,
  `articleId` ,
  `content` ,
  `addTime`
FROM `comment` LIMIT 0,500003

CREATE TABLE `comment2` (
  `id` INT(8) NOT NULL AUTO_INCREMENT,
  `blogUser` VARCHAR(20) NOT NULL,
  `replayUser` VARCHAR(20) NOT NULL,
  `articleId` INT(8) NOT NULL DEFAULT '0',
  `content` TEXT,
  `addTime` DATETIME NOT NULL,
  PRIMARY KEY (`id`),
  KEY `addTime` (`addTime`),
  KEY `replayUser` (`replayUser`)
) ENGINE=MYISAM AUTO_INCREMENT=1 DEFAULT CHARSET=utf8

INSERT INTO comment1 SELECT  `id` ,
  `blogUser`,
  `replayUser`,
  `articleId` ,
  `content` ,
  `addTime`
FROM `comment` LIMIT 500003,60000000

CREATE TABLE `allcomment` (
  `id` INT(8) NOT NULL AUTO_INCREMENT,
  `blogUser` VARCHAR(20) NOT NULL,
  `replayUser` VARCHAR(20) NOT NULL,
  `articleId` INT(8) NOT NULL DEFAULT '0',
  `content` TEXT,
  `addTime` DATETIME NOT NULL,
  PRIMARY KEY (`id`),
  KEY `addTime` (`addTime`),
  KEY `replayUser` (`replayUser`)
) ENGINE=MERGE UNION (comment1, comment2) INSERT_METHOD=LAST AUTO_INCREMENT=1 ; 

SELECT COUNT(*) FROM `allcomment`