Mysql 考虑到以前的订阅日，如何获得每日活跃用户？

我正在使用MySQL对订户进行一些数据分析，我想整理一下自服务启动以来每天活跃的订户。 我有一个订阅表，如下所示

id | subscriptiondate | unsubscriptiondate
---|------------------|--------------------
1  | 2020-02-12       | null
---|------------------|--------------------
2  | 2020-03-20       | 2020-04-01
---|------------------|--------------------
3  | 2020-03-10       | null
---|------------------|--------------------
4  |2020-04-02        | null

我期望的结果是：

date       | active_user
-----------|---------------------------
2020-02-12 | 1
-----------|------------------
2020-03-10 | 2
-----------|------------------
2020-03-20 | 3
-----------|------------------
2020-04-02 | 3

一个用户选择了2020-04-01，这就是为什么我们有3个活跃用户2020-04-02

这是我的SQL脚本，有人可以检查并帮助我实现我的目标吗

SELECT
    COUNT(distinct is) AS active_user,
    date(subscriptiondate) as day
FROM
    subscriptions
WHERE
        subscriptiondate in (select subscriptiondate  from subscriptions where subscriptiondate <=date(subscriptiondate))
    AND (unsubscriptiondate is NULL or unsubscriptiondate>date(subscriptiondate))
GROUP BY
    day
ORDER BY day ASC*

---

您可以取消拆分该表，并使用累计总和进行聚合：

select date, sum(inc) as change_on_date,
       sum(sum(inc)) over (order by date) as active_on_day
from ((select subscriptiondate as date, 1 as inc from subscriptions
      ) union all
      (select unsubscriptiondate, -1 from subscriptions
      )
     ) s
group by date;

---

您可以取消拆分该表，并使用累计总和进行聚合：

select date, sum(inc) as change_on_date,
       sum(sum(inc)) over (order by date) as active_on_day
from ((select subscriptiondate as date, 1 as inc from subscriptions
      ) union all
      (select unsubscriptiondate, -1 from subscriptions
      )
     ) s
group by date;