SQL - Adding conditions to SELECT - sql

Question

I have a table which has a timestamp and inCycle status of a machine. I'm using two CTE's and doing an INNER JOIN on row number so I can easily compare the timestamp of one row to the next. I have the DATEDIFF working and now I need to look at the inCycle status. Basically, if the inCycleThis and inCycleNext both = 1, I need to add it to an InCycle total.
Similarly (Shown table will make this clear):
incycleThis/next = 0,1 = not in cycle
incycleThis/next = 0,0 = not in cycle
incycleThis/next = 1,1 = in cycle
If I was doing this client side, this would be pretty simple. I need to do this in a stored procedure though due to there being a lot of records. I'd love to use an 'IF' in the SELECT section, but it seems that's not how it works.
The result I'm looking for at the end is simply: InCycle = Xtime. Something like:
SUM(Diff_seconds if((InCycleThis = 1 AND InCycleNext = 1) OR (InCycleThis = 1 AND InCycleNext = 0))
This is what I have so far:
WITH History_CTE (DT, MID, FRO, IC, RowNum)
AS
(
SELECT DateAndTime
,MachineID
,FeedRateOverride
,InCycle
,ROW_NUMBER()OVER(ORDER BY MachineID, DateAndTime) AS "row number"
FROM History
WHERE DateAndTime >= '2020-11-15'
AND DateAndTime < '2020-11-16'
),
History2_CTE (DT2, MID2, FRO2, IC2, RowNum2)
AS
(
SELECT DateAndTime
,MachineID
,FeedRateOverride
,InCycle
,ROW_NUMBER()OVER(ORDER BY MachineID, DateAndTime) AS "row number"
FROM History
WHERE DateAndTime >= '2020-11-15'
AND DateAndTime < '2020-11-16'
)
SELECT DT as 'TimeStamp'
,DT2 as 'TimeStamp Next Row'
,MID
,FRO
,IC as 'InCycle this'
,IC2 as 'InCycle next'
,RowNum
,DATEDIFF(s, History2_CTE.DT2, History_CTE.DT) AS 'Diff_seconds'
FROM History_CTE
INNER JOIN
History2_CTE ON History_CTE.RowNum = History2_CTE.RowNum2 + 1

Answer 1

Consider adding a third CTE to first conditionally calculate your needed value. Then aggregate for final statement. Recall CTEs can reference previously defined CTEs. Be sure to always quailfy columns with table aliases in JOIN queries.
WITH
... first two ctes...
, sub AS (
SELECT h1.DT AS 'TimeStamp'
, h2.DT2 AS 'TimeStamp Next Row'
, h1.MID
, h1.FRO
, h1.IC AS 'InCycle this'
, h2.IC2 AS 'InCycle next'
, h1.RowNum
, DATEDIFF(s, h2.DT2, h1.DT) AS 'Diff_seconds'
, CASE
WHEN (h1.IC = 1 AND h2.IC2 = 1) OR (h1.IC= 1 AND h2.IC2 = 0)
THEN DATEDIFF(s, h2.DT2, h1.DT)
END AS 'IC_Diff_seconds'
FROM History_CTE h1
INNER JOIN History2_CTE h2
ON h1.RowNum = h2.RowNum2 + 1
)
SELECT SUM([Diff_seconds]) AS Diff_seconds_Total
, SUM([IC_Diff_seconds]) AS IC_Diff_seconds_Total
FROM sub
And if needing to add groupings, incorporate GROUP BY:
SELECT h1.MID
, h1.FRO
, SUM([Diff_seconds]) AS Diff_seconds_Total
, SUM([IC_Diff_seconds]) AS IC_Diff_seconds_Total
FROM sub
GROUP BY h1.MID
, h1.FRO
Even aggregate calculations by day:
SELECT CONVERT(date, [TimeStamp]) AS [Day]
, SUM([Diff_seconds]) AS Diff_seconds_Total
, SUM([IC_Diff_seconds]) AS IC_Diff_seconds_Total
FROM sub
GROUP BY CONVERT(date, [TimeStamp])

Answer 2

The result I'm looking for at the end is simply: InCycle = Xtime. Something like:
SUM(Diff_seconds if((InCycleThis = 1 AND InCycleNext = 1) OR (InCycleThis = 1 AND InCycleNext = 0))
As I understand your question, you just need to sum the difference betwen the timestamp of "in cycle" rows and the timestamp of the next row.
select machineid,
sum(datediff(s, dateandtime, lead_dateandtime)) as total_in_time
from (
select h.*,
lead(dateandtime) over(partition by machineid order by dateandtime) as lead_dateandtime
from history h
) h
where inclycle = 1
group by machineid