SQL - How to sum revenue by customer over the last 7 days for each date - sql

Question

I want to sum the previous 7 days revenue from each date for each customer. There are some missing dates for some customers and various different customers so I cannot use a Lag function. I was previously using windows but I could only partition by customer_ID and could not partition by the date range as well.
Some sample data as follows:
Customer_ID
Date
Revenue
1
01/02/21
$20
2
01/02/21
$30
1
02/02/21
$40
2
02/02/21
$50
1
03/02/21
$20
2
03/02/21
$60
1
04/02/21
$10
2
04/02/21
$80
1
05/02/21
$100
2
05/02/21
$40
1
06/02/21
$20
2
06/02/21
$30
1
07/02/21
$50
2
07/02/21
$70
1
08/02/21
$10
2
08/02/21
$20
1
09/02/21
$3
2
09/02/21
$40
This result would give the sum of the previous seven days revenue broken down by customer ID for each date. It is ordered by Customer_ID and Date
Customer_ID
Date
Revenue
1
01/02/21
$20
1
02/02/21
$60
1
03/02/21
$80
1
04/02/21
$90
1
05/02/21
$190
1
06/02/21
$210
1
07/02/21
$260
1
08/02/21
$250
1
09/02/21
$240
2
01/02/21
$30
2
02/02/21
$80
2
03/02/21
$140
2
04/02/21
$220
2
05/02/21
$260
2
06/02/21
$290
2
07/02/21
$360
2
08/02/21
$350
2
09/02/21
$340
Data:
Database table
Query Result:
Query Result

Answer 1

select customer_id,date,sum(revenue) from customer_table where date >= sysdate-7 and date < =sysdate group by customer_id,date;
Hope this helps you

Answer 2

You can try going with a self join, where you match on:
tab1.customer_id = table2.customer_id
tab1.date being matched with till-6-days-before records of tab2.date.
Then apply the SUM on t2.revenues and aggregate on the selected fields.
SELECT t1.Customer_ID,
t1.Date,
SUM(t2.Revenue) AS total
FROM tab t1
LEFT JOIN tab t2
ON t1.Customer_ID = t2.Customer_ID
AND t1.Date BETWEEN t2.Date AND DATEADD(day, -6, t2.Date)
GROUP BY t1.Customer_ID,
t1.Date
This approach would avoid the issue of missing dates for customers, as long as you are comparing dates instead of taking the "last 7 records" with LAG.

Answer 3

with cte as (-- Customer_ID Date Revenue
select 1 customer_id, DATE( '01/02/2021','DD/MM/YYYY') Some_date, 20 Revenue
union all select 2 customer_id, DATE( '01/02/2021','DD/MM/YYYY') Some_date, 30 Revenue
union all select 1 customer_id, DATE( '03/02/2021','DD/MM/YYYY') Some_date, 20 Revenue
union all select 2 customer_id, DATE( '03/02/2021','DD/MM/YYYY') Some_date, 60 Revenue
union all select 1 customer_id, DATE( '04/02/2021','DD/MM/YYYY') Some_date, 10 Revenue
union all select 2 customer_id, DATE( '04/02/2021','DD/MM/YYYY') Some_date, 80 Revenue
union all select 1 customer_id, DATE( '05/02/2021','DD/MM/YYYY') Some_date, 100 Revenue
union all select 2 customer_id, DATE( '05/02/2021','DD/MM/YYYY') Some_date, 40 Revenue
union all select 1 customer_id, DATE( '06/02/2021','DD/MM/YYYY') Some_date, 20 Revenue
union all select 2 customer_id, DATE( '06/02/2021','DD/MM/YYYY') Some_date, 30 Revenue
union all select 1 customer_id, DATE( '07/02/2021','DD/MM/YYYY') Some_date, 50 Revenue
union all select 2 customer_id, DATE( '07/02/2021','DD/MM/YYYY') Some_date, 70 Revenue
union all select 1 customer_id, DATE( '08/02/2021','DD/MM/YYYY') Some_date, 10 Revenue
union all select 2 customer_id, DATE( '08/02/2021','DD/MM/YYYY') Some_date, 20 Revenue
union all select 1 customer_id, DATE( '09/02/2021','DD/MM/YYYY') Some_date, 3 Revenue
union all select 1 customer_id, DATE( '02/02/2021','DD/MM/YYYY') Some_date, 40 Revenue
union all select 2 customer_id, DATE( '02/02/2021','DD/MM/YYYY') Some_date, 50 Revenue
union all select 2 customer_id, DATE( '09/02/2021','DD/MM/YYYY') Some_date, 40 Revenue)
select customer_id, revenue
, DATE_TRUNC('week', Some_date ) week_number
, sum(revenue)
over(partition by customer_id,week_number
order by Some_date asc
rows between unbounded preceding and current row) volia
from cte