Sum over range but reset when other column value is 1 - sql

Question

So I have an account number and a reading number that I want to take the cumulative sum of but reset at the beginning of a new reading cycle (I want to reset the running sum).
I am using a window function but cannot figure out how to set it when the new reading cycle exists.
Data has the following format:
The Reading cycle Volume value is what I am attempting to achieve.
Currently I have tried SUM(Value) OVER(PARTITION BY ACCOUNT ORDER BY OBS)
I do not know how to reset it when reading # = 1.
I have tried:
Case
when [Reading #] = 1 THEN value
ELSE SUM(Value) OVER(PARTITION BY ACCOUNT ORDER BY OBS)
END AS [Running Total]

Answer 1

If I understand the question correctly and the values, stored in the Obs and [Reading #] columns are without gaps, the next approach is an option:
Table:
SELECT *
INTO Data
FROM (VALUES
(1, 1, 1, 5),
(1, 2, 2, 6),
(1, 3, 3, 5),
(1, 4, 4, 6),
(1, 5, 5, 5),
(1, 6, 6, 5),
(1, 7, 1, 5),
(1, 8, 2, 6),
(1, 9, 3, 5),
(1, 10, 4, 6),
(1, 11, 5, 5),
(1, 12, 6, 5),
(2, 1, 1, 7),
(2, 2, 2, 8),
(2, 3, 3, 9),
(2, 4, 4, 10),
(2, 5, 5, 11),
(2, 6, 6, 12),
(2, 7, 1, 7),
(2, 8, 2, 8),
(2, 9, 3, 9),
(2, 10, 4, 10),
(2, 11, 5, 11),
(2, 12, 6, 12)
) v (Account, Obs, [Reading #], [Value])
Statement:
SELECT
Account, Obs, [Reading #], [Value],
SUM([Value]) OVER (PARTITION BY Account, [Group] ORDER BY Account, Obs) AS [Ready Cicle Value]
FROM (
SELECT
*,
(Obs - [Reading #]) AS [Group]
FROM Data
) t
One additional option (as a more general approach) is to create groups when [Reading #] is equal to 1:
SELECT
Account, Obs, [Reading #], [Value],
SUM([Value]) OVER (PARTITION BY Account, [Group] ORDER BY Obs) AS [Ready Cicle Value]
FROM (
SELECT *, SUM([Change]) OVER (PARTITION BY Account ORDER BY Obs) AS [Group]
FROM (
SELECT *, CASE WHEN [Reading #] = 1 THEN 1 ELSE 0 END AS [Change]
FROM Data
) a
) b

Answer 2

Help us to help you. Always include a minimal set of data and the code we need, which we can copy and paste to immediately be on the same page as you without wasting time & effort that is better spent helping others. Note how you can simply copy and paste our solutions and play with them? They are complete and stand alone. That is what we are looking for from you.
You are close. The piece you are missing is that you need some way to group your readings and then you can include that in your partitioning as well.
There are any number of ways to create the new derived value for "reading_group" the following is just one way.
DECLARE #t_customer_readings TABLE
( account_number INT,
observation INT,
reading_number INT,
reading_value INT
)
INSERT INTO #t_customer_readings
VALUES (1, 1 , 1, 3),
(1, 2 , 2, 6),
(1, 3 , 3, 9),
(1, 4 , 4, 5),
(1, 5 , 5, 5),
(1, 6 , 6, 8),
(1, 7 , 1, 1),
(1, 8 , 2, 4),
(1, 9 , 3, 7),
(1, 10, 4, 0),
(1, 11, 5, 3),
(1, 12, 6, 6),
(2, 1 , 1, 9),
(2, 2 , 2, 2),
(2, 3 , 3, 5),
(2, 4 , 4, 8),
(2, 5 , 5, 1),
(2, 6 , 6, 4),
(2, 7 , 1, 7),
(2, 8 , 2, 0),
(2, 9 , 3, 3),
(2, 10, 1, 6), -- note I have split this group into 2 to show that the reading numbers do not need to be sequential.
(2, 11, 5, 9),
(2, 12, 6, 2)
SELECT r.*,
-- reading_group = CASE WHEN r.reading_number = 1 THEN observation ELSE rg.reading_group END,
ready_cycle_volume = SUM(reading_value) OVER(PARTITION BY account_number,
CASE WHEN r.reading_number = 1 THEN observation
ELSE rg.reading_group
END
ORDER BY observation)
FROM #t_customer_readings r
CROSS APPLY
(SELECT reading_group = MAX(observation) -- I picked observation but you could use whatever value you like. we are just creating something we can group on.
FROM #t_customer_readings
WHERE account_number = r.account_number
AND observation < r.observation
AND reading_number = 1) rg