Issue with Row_Number() Over Partition - sql

Question

I've been trying to reset the row_number when the value changes on Column Value and I have no idea on how should i do this.
This is my SQL snippet:
WITH Sch(SubjectID, VisitID, Scheduled,Actual,UserId,RLev,SubjectTransactionID,SubjectTransactionTypeID,TransactionDateUTC,MissedVisit,FieldId,Value) as
(
select
svs.*,
CASE WHEN stdp.FieldID = 'FrequencyRegime' and svs.SubjectTransactionTypeID in (2,3) THEN
stdp.FieldID
WHEN stdp.FieldID is NULL and svs.SubjectTransactionTypeID = 1
THEN NULL
WHEN stdp.FieldID is NULL
THEN 'FrequencyRegime'
ELSE stdp.FieldID
END AS [FieldID],
CASE WHEN stdp.Value is NULL and svs.SubjectTransactionTypeID = 1
THEN NULL
WHEN stdp.Value IS NULL THEN
(SELECT TOP 1 stdp.Value from SubjectTransaction st
JOIN SubjectTransactionDataPoint STDP on stdp.SubjectTransactionID = st.SubjectTransactionID and stdp.FieldID = 'FrequencyRegime'
where st.SubjectID = svs.SubjectID
order by st.ServerDateST desc)
ELSE stdp.Value END AS [Value]
from SubjectVisitSchedule svs
left join SubjectTransactionDataPoint stdp on svs.SubjectTransactionID = stdp.SubjectTransactionID and stdp.FieldID = 'FrequencyRegime'
)
select
Sch.*,
CASE WHEN sch.Value is not NULL THEN
ROW_NUMBER() over(partition by Sch.Value, Sch.SubjectID order by Sch.SubjectID, Sch.VisitID)
ELSE NULL
END as [FrequencyCounter],
CASE WHEN Sch.Value = 1 THEN 1--v.Quantity
WHEN Sch.Value = 2 and (ROW_NUMBER() over(partition by Sch.Value, Sch.SubjectID order by Sch.SubjectID, Sch.VisitID) % 2) <> 0
THEN 0
WHEN Sch.Value = 2 and (ROW_NUMBER() over(partition by Sch.Value, Sch.SubjectID order by Sch.SubjectID, Sch.VisitID) % 2) = 0
THEN 1
ELSE NULL
END AS [DispenseQuantity]
from Sch
--left join VisitDrugAssignment v on v.VisitID = Sch.VisitID
where SubjectID = '4E80718E-D0D8-4250-B5CF-02B7A259CAC4'
order by SubjectID, VisitID
This is my Dataset:
Based on the Dataset, I am trying to reset the FrequencyCounter to 1 every time the value changes for each subject, Right now it does 50% of what I want, It is counting when the value 1 or 2 is found, but when value 1 comes again after value 2 it continues the count from where it left. I want every time the value is changes the count to also start from the beginning.

Answer 1

It's difficult to reproduce and test without sample data, but if you want to know how to number rows based on change in column value, next approach may help. It's probably not the best one, but at least will give you a good start. Of course, I hope I understand your question correctly.
Data:
CREATE TABLE #Data (
[Id] int,
[Subject] varchar(3),
[Value] int
)
INSERT INTO #Data
([Id], [Subject], [Value])
VALUES
(1, '801', 1),
(2, '801', 2),
(3, '801', 2),
(4, '801', 2),
(5, '801', 1),
(6, '801', 2),
(7, '801', 2),
(8, '801', 2)
Statement:
;WITH ChangesCTE AS (
SELECT
*,
CASE
WHEN LAG([Value]) OVER (PARTITION BY [Subject] ORDER BY [Id]) <> [Value] THEN 1
ELSE 0
END AS [Change]
FROM #Data
), GroupsCTE AS (
SELECT
*,
SUM([Change]) OVER (PARTITION BY [Subject] ORDER BY [Id]) AS [GroupID]
FROM ChangesCTE
)
SELECT
*,
ROW_NUMBER() OVER (PARTITION BY [GroupID] ORDER BY [Id]) AS Rn
FROM GroupsCTE
Result:
--------------------------------------
Id Subject Value Change GroupID Rn
--------------------------------------
1 801 1 0 0 1
2 801 2 1 1 1
3 801 2 0 1 2
4 801 2 0 1 3
5 801 1 1 2 1
6 801 2 1 3 1
7 801 2 0 3 2
8 801 2 0 3 3

Answer 2

As per my understanding, you need DENSE_RANK as you are looking for the row number will only change when value changed. The syntax will be as below-
WITH your_table(your_column)
AS
(
SELECT 2 UNION ALL
SELECT 10 UNION ALL
SELECT 2 UNION ALL
SELECT 11
)
SELECT *,DENSE_RANK() OVER (ORDER BY your_column)
FROM your_table