public function getLast(): array
    {
        $sql = "select migration from {$this->table} as b
                where exists (select max(batch) from {$this->table} as a where b.batch = a.batch) 
                order by migration desc";

        $stmt = $this->pdo->prepare($sql);
        $stmt->execute();

        return $stmt->fetchAll(PDO::FETCH_COLUMN);
    }