CREATE TABLE `statistic` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `date_end` datetime(6) NOT NULL,
  `date_start` datetime(6) NOT NULL,
  PRIMARY KEY (`id`),
  KEY `statistic_date_end_6f3de8e3933125c_uniq` (`date_end`),
  KEY `statistic_date_start_35e1f6a6a8caae3_uniq` (`date_start`)
) ENGINE=MyISAM AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;

SELECT COUNT(`out`.`id`)
FROM `statistic` AS `out`
WHERE EXISTS(
    SELECT *
    FROM `statistic_prolonged` AS `in`
    WHERE (
        `out`.`date_end` <= `in`.`date_start`
        AND `in`.`date_end` <= `out`.`date_start`
    )
);

create view `change` as
select date_start `date`,  1 `value` from statistic
union all
select date_end         , -1         from statistic;

select c2.`date` `date`, sum(c1.`value`) conn_amount
from change c1, change c2
where c1.`date` <= c2.`date`
group by c2.`date`;