range between interval that does not include the first row - sql

Question

I have a line:
sum(purchases) over(partition by category order by value_day range between interval '1' month preceding and current row)
If value_day = Aug 21, it returns sum from and included July 21 till and included Aug 21, but I need from and included July 22 till and included Aug 21.
How can I do that?

Answer 1

You can use an expression to define the starting point of the window. So you can
Subtract a month from the current date
Add a day to it
Giving something like:
sum ( purchases ) over (
partition by category
order by value_day
range between ( value_day - ( add_months ( value_day, -1 ) + 1 ) ) preceding
and current row
)

Answer 2

You can either:
Use two windowed functions, your one to add everything from the past month and then subtract a second one that just covers the range you do not want to include; or
Use a correlated sub-query rather than windowed analytic functions.
SELECT t.*,
sum(purchases) over(
partition by category
order by value_day
range between interval '1' month preceding and current row
) -
COALESCE(
sum(purchases) over(
partition by category
order by value_day
range between interval '1' month preceding and interval '1' month preceding
),
0
) AS total1,
( SELECT SUM(s.purchases)
FROM table_name s
WHERE t.category = s.category
AND ADD_MONTHS(t.value_day, -1) + INTERVAL '1' DAY <= s.value_day
AND s.value_day <= t.value_day
) AS total2
FROM table_name t;
Which, for the sample data:
CREATE TABLE table_name (category, value_day, purchases) AS
SELECT 1, DATE '2022-01-01' + LEVEL - 1, LEVEL
FROM DUAL
CONNECT BY LEVEL <= 50;
Outputs:
CATEGORY
VALUE_DAY
PURCHASES
TOTAL1
TOTAL2
...
...
...
...
...
1
01-FEB-22
32
527
527
1
02-FEB-22
33
558
558
1
03-FEB-22
34
589
589
1
04-FEB-22
35
620
620
1
05-FEB-22
36
651
651
1
06-FEB-22
37
682
682
1
07-FEB-22
38
713
713
1
08-FEB-22
39
744
744
1
09-FEB-22
40
775
775
1
10-FEB-22
41
806
806
1
11-FEB-22
42
837
837
1
12-FEB-22
43
868
868
1
13-FEB-22
44
899
899
1
14-FEB-22
45
930
930
1
15-FEB-22
46
961
961
1
16-FEB-22
47
992
992
1
17-FEB-22
48
1023
1023
1
18-FEB-22
49
1054
1054
1
19-FEB-22
50
1085
1085
db<>fiddle here