Помогите выпольнить SQL запрос

 
 
    $inDB   = cmsDatabase::getInstance();
 
    for ($i = 1; $i < 2000000; $i++) {
        set_time_limit(30);
 
        $item = array(
            'nickname' => "user_{$i}",
            "login" => "user_{$i}",
        );
        $inDB->insert('cms_users', $item);
    }
 
 

 
 
class RandomUser {
 
    private $db;
    private $limit;
    private $usersTableName = 'cms_users';
    private $users = array();
 
    public function __construct($limit) {
 
        $this->db = cmsDatabase::getInstance();
        $this->limit = $limit;
    }
 
    public function getUsers() {
 
        $usersIds = array();
        $maxId = $this->getMaxId();
        for ($i = 0; $i < $this->limit; $i++) {
 
            // получаем рандомный Id
            $randomId = mt_rand(0, $maxId);
 
            // составляем sql запрос
            $sql = "SELECT id, nickname FROM {$this->usersTableName} AS u WHERE id >= {$randomId}";
 
            // одного пользователя можно достать только 1 раз
            $sql .= $usersIds ? ' AND id NOT IN (' . implode(',', $usersIds) . ')' : '';
            $sql .= " ORDER BY id ASC LIMIT 1";
 
            $user = $this->db->query($sql)->fetch_object();
 
            $usersIds[] = $user->id;
 
            $this->users[] = $user;
        }
 
        return $this->users;
    }
 
    public function getUsersBadMethod() {
 
        $sql = "SELECT id, nickname FROM {$this->usersTableName} ORDER BY RAND() LIMIT {$this->limit}";
        $result = $this->db->query($sql);
 
        while($user = $this->db->fetch_assoc($result)) {
            $this->users[] = $user;
        }
 
        return $this->users;
    }
 
    /**
     * @return int - максимальный (последний) Id пользователя
     */
    private function getMaxId() {
 
        $sql = "SELECT MAX(id) as maxId FROM {$this->usersTableName}";
        return $this->db->query($sql)->fetch_object()->maxId;
    }
}
 
 

 
 
class Timer {
 
    private $startTime;
 
    private function getTime() {
 
        list($usec, $seconds) = explode(' ', microtime());
        return ((float) $usec + (float) $seconds);
    }
 
    function start() {
 
        $this->startTime = $this->getTime();
    }
 
    function end() {
 
        return ($this->getTime() - $this->startTime);
    }
}
 
 

 
 
    $timer = new Timer();
 
    $timer->start();
    $randomUser = new RandomUser(10);
    $users = $randomUser->getUsers();
    $time1 = $timer->end();
 
    $timer->start();
    $randomUser = new RandomUser(10);
    $users = $randomUser->getUsersBadMethod();
    $time2 = $timer->end();
 
 
    echo "Time 1: " . number_format($time1, 4) . ' sec';
    echo '<br />';
    echo "Time 2: " . number_format($time2, 4) . ' sec';
 
 

 
WHERE id >= {$randomId}
 

 
    $sql = "SELECT id, nickname FROM {$this->usersTableName} AS u WHERE id >= {$randomId}";
 

 
     ..WHERE id < {$randomId}