protected static function checkColumn($tableName, $columnName, $con=NULL)
    {
        $connection = self::checkConnection($con);

            $result = $connection->prepare("SELECT {$columnName} FROM {$tableName}");
            $result->execute();
            if (! $result->columnCount())
            {
                throw new ColumnNotExistExeption();
            }
            return $columnName;
    }