我想创建一个查询来按月获取我们活跃客户的累积总和。这里的棘手之处在于(不幸的是)一些客户流失了,所以我需要在他们离开我们的当月将他们从累积金额中删除。
这是我的客户表的示例:
customer_id | begin_date | end_date
-----------------------------------------
1 | 15/09/2017 |
2 | 15/09/2017 |
3 | 19/09/2017 |
4 | 23/09/2017 |
5 | 27/09/2017 |
6 | 28/09/2017 | 15/10/2017
7 | 29/09/2017 | 16/10/2017
8 | 04/10/2017 |
9 | 04/10/2017 |
10 | 05/10/2017 |
11 | 07/10/2017 |
12 | 09/10/2017 |
13 | 11/10/2017 |
14 | 12/10/2017 |
15 | 14/10/2017 |
这是我想要实现的目标:
month | active customers
-----------------------------------------
2017-09 | 7
2017-10 | 6
我已经设法通过以下查询实现了它......但是,我想知道是否有更好的方法。
select
"begin_date" as "date",
sum((new_customers.new_customers-COALESCE(churn_customers.churn_customers,0))) OVER (ORDER BY new_customers."begin_date") as active_customers
FROM (
select
date_trunc('month',begin_date)::date as "begin_date",
count(id) as new_customers
from customers
group by 1
) as new_customers
LEFT JOIN(
select
date_trunc('month',end_date)::date as "end_date",
count(id) as churn_customers
from customers
where
end_date is not null
group by 1
) as churn_customers on new_customers."begin_date" = churn_customers."end_date"
order by 1
;