<?php
$dsn = 'mysql:host=localhost;dbname=onetest';
$options = array(
    PDO::MYSQL_ATTR_INIT_COMMAND => 'SET NAMES utf8mb4',
);
$db = new \PDO($dsn, 'root','', $options);
$sql="SELECT * FROM serials";
$r=$db->query($sql,PDO::FETCH_ASSOC)->fetch();
print_r($r);
echo date('H:i:s')."\r\n";
$f=fopen('1.csv', 'w');
for($i=0;$i<750000;$i++)
{
    $r=random_int(1000000,9999999);
    $sql="INSERT INTO `serials`(`year`, `digit`, `serial`) VALUES (19, 12, $r)";
    $db->query($sql);
    fputs($f, '19;12;'.$r."\r\n");
}
fclose($f);
echo date('H:i:s')."\r\n";