MS SQL value change - sql-server

Question

I have a SQL query that looks like this.
Select Timestamp, Value From [dbo].[nro_ReadRawDataByTimeFunction](
'SV/SVTP01.BONF0335-D1-W1-BL1',
'2017-11-01 00:00',
'2017-12-01 00:00')
GO
This will return
Timestamp | Value
1 2017-11-01 10:00 | 0
2 2017-11-01 11:00 | 0
3 2017-11-01 12:00 | 0
4 2017-11-01 13:00 | 1
5 2017-11-01 14:00 | 1
6 2017-11-01 15:00 | 0
7 2017-11-01 16:00 | 0
8 2017-11-01 17:00 | 0
9 2017-11-01 18:00 | 1
10 2017-11-01 19:00 | 0
The full list is alot larger, and I'm only interested in in results where value change from last result, so in this case row 1,4,6,9,10
I know how to do it if it's directly from a table but not when it's from a function

Answer 1

You can use this construction:
;WITH cte AS (
Select [Timestamp],
[Value]
From [dbo].[nro_ReadRawDataByTimeFunction](
'SV/SVTP01.BONF0335-D1-W1-BL1',
'2017-11-01 00:00',
'2017-12-01 00:00')
)
SELECT TOP 1 WITH TIES c.*
FROM cte c
OUTER APPLY (
SELECT TOP 1 *
FROM cte
WHERE [Value] != c.[Value] AND c.[Timestamp] < [Timestamp]
ORDER BY [Timestamp] ASC
) t
ORDER BY ROW_NUMBER() OVER (PARTITION BY t.[Timestamp] ORDER BY c.[Timestamp] ASC)
Output:
Timestamp Value
2017-11-01 19:00 0
2017-11-01 10:00 0
2017-11-01 13:00 1
2017-11-01 15:00 0
2017-11-01 18:00 1
Explanation:
SELECT *
FROM cte c
OUTER APPLY (
SELECT TOP 1 *
FROM cte
WHERE [Value] != c.[Value] AND c.[Timestamp] < [Timestamp]
ORDER BY [Timestamp] ASC
) t
Here we select data from main table and with the help of OUTER APPLY add to each row data with different value and greater timestamp.
ROW_NUMBER() OVER (PARTITION BY t.[Timestamp] ORDER BY c.[Timestamp] ASC)
Hope, you are familiar with ROW_NUMBER it
returns the sequential number of a row within a partition of a result set, starting at 1 for the first row in each partition.
So, if you run the above query and add this code to SELECT, you will get:
Timestamp Value Timestamp Value rn
2017-11-01 19:00 0 NULL NULL 1
2017-11-01 10:00 0 2017-11-01 13:00 1 1
2017-11-01 11:00 0 2017-11-01 13:00 1 2
2017-11-01 12:00 0 2017-11-01 13:00 1 3
2017-11-01 13:00 1 2017-11-01 15:00 0 1
2017-11-01 14:00 1 2017-11-01 15:00 0 2
2017-11-01 15:00 0 2017-11-01 18:00 1 1
2017-11-01 16:00 0 2017-11-01 18:00 1 2
2017-11-01 17:00 0 2017-11-01 18:00 1 3
2017-11-01 18:00 1 2017-11-01 19:00 0 1
As you can see, all rows you need are marked with 1. We coluld put this in other CTE or sub-query and use rn = 1 but we can do it all-in-one with the help of TOP 1 WITH TIES (MSDN link).

Answer 2

Since you are referring to SQL Server 2012 you can enjoy the new features:
;WITH Hist AS (
SELECT r,
LAG(v) OVER(ORDER BY d) PreviousValue,
v,
LEAD(v) OVER(ORDER BY d) NextValue ---Just to know that also this is available
FROM #t
)
SELECT *
FROM Hist h Inner JOIN #t t ON h.r = t.r
WHERE ISNULL(h.PreviousValue, -1) != t.v
#t contains your results

Answer 3

If this function is a table-valued function, you can just put it in the where or do it inside a function, in this second case as a parameter?
Select a.Timestamp, a.Value From [dbo].[nro_ReadRawDataByTimeFunction](
'SV/SVTP01.BONF0335-D1-W1-BL1',
'2017-11-01 00:00',
'2017-12-01 00:00') as a
WHERE a.Value = 1

Answer 4

What i ended with is as following
#DECLARE #startDate DATE,
#tagName nVarChar(200);
WITH CTE AS(
SELECT Timestamp As StopTime, Value As [OFF], LAG(Value,1) OVER (order by Timestamp) As [ON], Quality
FROM [dbo].[nrp_ReadRawDataByTimeFunction] (#TagName,#startDate, DATEADD(MONTH,2,#startDate))
Where Quality & 127 = 100
),
CalenderCTE AS(
SELECT [DATE] = DATEADD(Day,Number,#startDate)
FROM master..spt_values
WHERE Type='P'
AND DATEADD(day,Number,#startDate) < DATEADD(MONTH,1,#startDate)
)
SELECT * FROM CTE
FULL OUTER JOIN
CalenderCTE on CalenderCTE.Date = CAST(CTE.StopTime as [Date])
Where CTE.[OFF] != CTE.[ON}
This is just a tiny part of the query since it doing alot more which ain't included in the original post.
Thanks all for your input's, it help me on the way to the final result.