public function unixTimestamp( $column )
    {
        $column = $this->getIdentifier( $column );

        if ( $column != 'NOW()' )
        {
            $column = "CAST( {$column} AS TIMESTAMP )";
//            // alternative
//            if ( preg_match( '/[0-9]{4}-[0-9]{2}-[0-9]{2} [0-9]{2}:[0-9]{2}:[0-9]{2}/', $column ) ) {
//                $column = "TO_TIMESTAMP( {$column}, 'YYYY-MM-DD HH24:MI:SS' )";
//            }
        }

        $date1 = "CAST( SYS_EXTRACT_UTC( {$column} ) AS DATE )";
        $date2 = "TO_DATE( '19700101000000', 'YYYYMMDDHH24MISS' )";
        return " ROUND( ( {$date1} - {$date2} ) / ( 1 / 86400 ) ) ";
    }