SQL - Need return from single table of SUMs over 3 different date ranges - sql

Question

I have a table of Account Transactions that includes ID, Amount, Date. Basically, I want to create a resulting table that looks at the table and returns what the SUM was for the Account over three different Ending Date Ranges. Then I want to Flag (Combined_Flag) each Account ID, 1 if any of the SUMs for that ID are non-zero, and a 0 if all of the SUMs are 0.
Date Range 1) Min Date to End of Last Month (-1 Month)
Date Range 2) Min Date to End of 2 Months ago (-2 Months)
Date Range 3) Min Date to End of Last Month, Last Year (-13 Months)
The Resulting table should be: ID, SUM_R1, SUM_R2, SUM_R3, Flag_R1, Flag_R2, Flag_R3, Combined_Flag
Example Data
| ID | Amount | Date |
| -------- | -------------- |-------------- |
| 1 | 20 | 09/01/19 |
| 2 | 40 | 09/01/19 |
| 3 | 0 | 09/01/19 |
| 4 | 0 | 09/01/19 |
| 1 | 10 | 10/01/19 |
| 2 | 0 | 10/01/19 |
| 3 | 0 | 10/01/19 |
| 4 | 0 | 10/01/19 |
| 1 | 15 | 11/01/19 |
| 2 | 40 | 11/01/19 |
| 3 | 0 | 11/01/19 |
| 4 | 0 | 11/01/19 |
| 1 | 20 | 09/01/20 |
| 2 | 40 | 09/01/20 |
| 3 | 0 | 09/01/20 |
| 4 | 50 | 09/01/20 |
| 1 | 10 | 10/01/20 |
| 2 | 0 | 10/01/20 |
| 3 | 0 | 10/01/20 |
| 4 | 65 | 10/01/20 |
| 1 | 15 | 11/01/20 |
| 2 | 40 | 11/01/20 |
| 3 | 0 | 11/01/20 |
| 4 | 0 | 11/01/20 |
Expected Result Table (Using Date of 12/21/2020)
| ID | SUM_R1 | SUM_R2 | SUM_R3 | Flag_R1 | Flag_R2 | Flag_R3 | Combined_Flag |
| -------- | -------- | -------- | -------- | --------- | --------- | --------- | --------------- |
| 1 | 90 | 75 | 45 | 1 | 1 | 1 | 1 |
| 2 | 160 | 120 | 80 | 1 | 1 | 1 | 1 |
| 3 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| 4 | 115 | 115 | 0 | 1 | 1 | 0 | 1 |
The difficulty I'm having is in joining the table basically to itself 2 times. I'm getting results all over the place and not really sure exactly what's going on.

Answer 1

Is this what you want?
select id,
sum(case when date < datefromparts(year(v.dte), month(v.dte), 1)
then amount else 0
end) as sum_r1,
sum(case when date < dateadd(month, -1, datefromparts(year(v.dte), month(v.dte), 1))
then amount else 0
end) as sum_r2,
sum(case when date < dateadd(month, -13, datefromparts(year(v.dte), month(v.dte), 1))
then amount else 0
end) as sum_r3,
max(case when amount > 0 and date < datefromparts(year(v.dte), month(v.dte), 1)
then 1 else 0
end) as flag_r1,
max(case when amount > 0 and date < dateadd(month, -1, datefromparts(year(v.dte), month(v.dte), 1))
then 1 else 0
end) as flag_r2,
max(case when amount > 0 and date < dateadd(month, -13, datefromparts(year(v.dte), month(v.dte), 1))
then 1 else 0
end) as flag_r3
from t cross join
(values (convert(date, '2020-12-21'))
) v(dte)
group by id;
The flag columns assume that the amounts are never negative (which is consistent with the data in your question.
EDIT:
The shorthand in the comment for creating the flag looks like:
abs(sign(sum(case when amount > 0 and date < datefromparts(year(v.dte), month(v.dte), 1)
then amount else 0
end))) as flag_r1,
Here is a db<>fiddle.