public function getTableColumns() : array
    {
        if (!$this->isTableNameSet()) {
            return [];
        }
        
        $sql = "SHOW COLUMNS FROM `".$this->tableName."`";
        $stmt = $this->db->query($sql);
        $arrResult = $stmt->fetchAll(PDO::FETCH_ASSOC);
        return $arrResult;
    }