Running Total to the latest period - sql

Question

I want to query the table so that the running total is repeatedly
carrying over to the latest period as long as the value dose not fall to 0.
Assuming I have a table with values as such below:
Name
Period
Value
A
02/2022
2
A
03/2022
5
A
04/2022
3
A
05/2022
7
B
02/2022
9
B
04/2022
6
I want my result to be:
| Name | Period | Value|
| A| 02/2022| 2 |
| A| 03/2022| 7 |
| A| 04/2022| 10|
| A| 05/2022| 17|
| B| 02/2022| 9 |
| B| 03/2022| 9 |
| B| 04/2022| 15|
| B| 05/2022| 15|
My current query is:
SELECT
PERIOD
,NAME
,SUM(SUM(Value)) OVER (PARTITION BY NAME ORDER BY PERIOD) AS balance
FROM
table
WHERE Period < CURRENT_DATE()
GROUP BY
1
,2
This results in the value stopping at the latest period the activity occurred as such:
| Name | Period | Value|
| A | 02/2022| 2 |
| A | 03/2022| 7 |
| A | 04/2022| 10 |
| A | 05/2022| 17 |
| B | 02/2022| 9 |
| B | 04/2022| 15 |

Answer 1

OK, you haven't had an answer in a full day so even though I work in TSQL I'll try a solution that's ANSI SQL compatible. Work with me if my syntax is off a bit.
Before we start, check your "Desired Output", you're currently showing a running total for A on 3/22 of 5, but you had a 2 for A on 2/22 so it should be a running total of 7, right?
Anyway, assuming that's just a typo, I'd approach this by making a few CTEs that build a list of all {PERIOD, NAME} pairs you want reported, then JOIN your actual data to that. There are a number of ways to generate the dates, the easiest is to use DISTINCT if your actual data is fairly robust, but I can describe other methods if that assumption does not hold for your data.
So with all that in mind, here is my solution. I put your sample data in a CTE for portability, just replace my "cteTabA" with whatever your data table is really named
--Code sample data as a CTE for portability
;with cteTabA as (
SELECT *
FROM ( VALUES
('A', '02/2022', '2')
, ('A', '03/2022', '5')
, ('A', '04/2022', '3')
, ('A', '05/2022', '7')
, ('B', '02/2022', '9')
, ('B', '04/2022', '6')
) as TabA(Name, Period, Value)
) --END of sample data, actual query below
--First, build a list of periods to use. If your data set is full, just select DISTINCT
, cteDates as ( --but there are other ways if this doesn't work for you - let me know!
SELECT DISTINCT Period FROM cteTabA
) --Next, build a list of names to report on
, cteNames as (
SELECT DISTINCT Name FROM cteTabA
) --Now build your table that has all periods for all names
, cteRepOn as (
SELECT * FROM cteNames CROSS JOIN cteDates
)--Now assemble a table that has entries for each period for each name,
--but fill in zeroes for those you don't actually have data for
, cteFullList as (
SELECT L.*, COALESCE(D.Value, 0) as Value
FROM cteRepOn as L
LEFT OUTER JOIN cteTabA as D on L.Name = D.Name AND L.Period = D.Period
)--Now your query works as expected with the gaps filled in
SELECT PERIOD, NAME, Value
,SUM(Value) OVER (PARTITION BY NAME ORDER BY PERIOD) AS balance
FROM cteFullList
WHERE Period < '06/2022'--CURRENT_DATE()
ORDER BY NAME, PERIOD
This produces an output as follows
PERIOD
NAME
Value
balance
02/2022
A
2
2
03/2022
A
5
7
04/2022
A
3
10
05/2022
A
7
17
02/2022
B
9
9
03/2022
B
0
9
04/2022
B
6
15
05/2022
B
0
15