[英]Postgres cumulative count over time
我试图在一个月内找到一个月内活跃订阅的数量。
表:订阅字段:
在以下情况下,订阅在特定时间戳中被视为活动:
例:
这是我试过的:
select "Month", sum(sub) over (order by "Month" asc) as "Active subscriptions"
from
(select to_char(subscriptions."creationDate" at time zone '-7', 'YYYY-MM') as "Month",
count(distinct subscriptions.id) as sub
from subscriptions
where (to_char(subscriptions."deletionDate" at time zone '-7', 'YYYY-MM') is null
or to_char(subscriptions."deletionDate" at time zone '-7', 'YYYY-MM') >= to_char(subscriptions."creationDate" at time zone '-7', 'YYYY-MM') )
group by "Month") as foo
但是,问题在于它包含了上个月的非活动订阅数。 为了说明我的意思,我的上述查询似乎包括2014年7月的订阅B(在上面的示例中)作为有效订阅。
我不确定如何获取特定月份的“有效订阅”以删除前几个月不再有效的订阅数。
谢谢! :)
SELECT m, count(subscriptions.*)
FROM subscriptions
JOIN generate_series('2010-01-01'::date, now(), interval '1 mon') AS m
ON m >= subscriptions.creationDate AND
(subscriptions.deletionDate IS NULL OR m <= subscriptions.deletionDate)
/* You may get better indexed performance if you use a date
far in the future for current
accounts, instead of NULL. Then you can use BETWEEN */
GROUP BY m ORDER BY m;
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