[英]Postgres cumulative count over time
我試圖在一個月內找到一個月內活躍訂閱的數量。
表:訂閱字段:
在以下情況下,訂閱在特定時間戳中被視為活動:
例:
這是我試過的:
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,問題在於它包含了上個月的非活動訂閱數。 為了說明我的意思,我的上述查詢似乎包括2014年7月的訂閱B(在上面的示例中)作為有效訂閱。
我不確定如何獲取特定月份的“有效訂閱”以刪除前幾個月不再有效的訂閱數。
謝謝! :)
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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