Aggregating schedule data by start and end times - sql

Question

I have a tricky problem that has had me scratching my head for a little while. I have some data that represents the delivery of "widgets" over a variable number of days, broken down into half hourly slots.
For example (apologies for formatting - haven't quite got to grips with it):
Date Time NoOfUnits
01-Mar-2010 00:00 0
01-Mar-2010 00:30 0
01-Mar-2010 01:00 0
.... (following half hour intervals have NoOfUnits = 0)
01-Mar-2010 23:00 10
01-Mar-2010 23:30 10
02-Mar-2010 00:00 10
.... (following half hour intervals have NoOfUnits = 1)
02-Mar-2010 07:00 10
02-Mar-2010 07:30 0
.... (following half hour intervals have NoOfUnits = 0)
02-Mar-2010 23:30 0
I need to generate a query that will allow me to group this data into all the distinct blocks where I am delivering a unit. In the above example I need to identify only 1 block - 23:00 to 07:00, and the sum of units for that block (160). The required result would therefore be StartTime, EndTime, TotalNoOfUnits.
However, the complexity comes when we have different patterns of delivery - maybe we have a day where we deliver units for 24 hours.
I need to be able to query data in the format above and identify all the unique StartTime, EndTime and TotalNoOfUnits combinations where NoOfUnits <> 0.
Apologies again for formatting and a slightly rambling question. Please ask any questions you need for me to clarify things.
EDIT: Just to be clear, the data will always run from 00:00 to 23:30 for each day of delivery, and each half hour slot will always be present. It is only the number of days and unit per half hour slot that may vary for any given data set.
EDIT2: Below is a script that will populate a table with 2 days worth of schedule data. The schedule is the same for both days. The result I would expect to see, based on my requirements, would be 13:00, 00:00, 230. As you will see from the below my SQL skills are not great hence the head scratching!
declare #DayCount int
declare #HalfHourCount int
declare #HH int
declare #CurrentDate datetime
declare #BaseDate datetime
declare #NoOfUnits int
set #HalfHourCount = 48
set #DayCount = 4
set #BaseDate = '1 Jan 1900'
create table #Schedule
(
Date datetime
, Time datetime
, NoOfUnits int
)
while #DayCount > 0
begin
set #CurrentDate = dateadd(dd, #DayCount * -1, CONVERT(VARCHAR(10),GETDATE(),111))
set #HH = #HalfHourCount
while #HH > 0
begin
if #HH > 24
set #NoOfUnits = 10
else
begin
if #DayCount = 4 and #HH < 10
set #NoOfUnits = 10
else
set #NoOfUnits = 0
end
insert into #Schedule(Date, Time, NoOfUnits)
values (#CurrentDate, dateadd(mi, #HH / 2.0 * 60, #BaseDate), #NoOfUnits)
select #HH = #HH - 1
end
set #DayCount = #DayCount - 1
end
Expected result (although test data should start from 00:00 and go to 23:00 instead of 00:30 to 00:00):
StartTime TotalUnits EndDate
----------------------- ----------- -----------------------
1900-01-01 00:30:00.000 90 1900-01-01 04:30:00.000
1900-01-01 12:30:00.000 960 1900-01-02 00:00:00.000

Answer 1

This should work, based on the data you have provided. It can almost certainly be simplified:
;WITH dateCTE
AS
(
SELECT *
,date + [time] dt
FROM #Schedule
)
,seqCTE
AS
(
SELECT NoOfUnits
,dt
,ROW_NUMBER() OVER (ORDER BY dt) AS rn
FROM dateCTE
)
,recCTE
AS
(
SELECT NoOfUnits
,dt
,1 AS SEQUENCE
,rn
FROM seqCTE
WHERE rn = 1
UNION ALL
SELECT s.NoOfUnits
,s.dt
,CASE WHEN (s.NoOfUnits > 0
AND r.NoOfUnits > 0
)
OR (s.NoOfUnits = 0
AND r.NoOfUnits = 0
)
THEN r.SEQUENCE
ELSE r.SEQUENCE + 1
END
,s.rn
FROM recCTE AS r
JOIN seqCTE AS s
ON s.rn = r.rn + 1
)
,summaryCTE
AS
(
SELECT RIGHT(CONVERT(varchar(23),MIN(dt),120),8) AS startTime
,RIGHT(CONVERT(varchar(23),MAX(dt),120),8) AS endTime
,SUM(NoOfUnits) AS NoOfUnits
FROM recCTE
GROUP BY SEQUENCE
HAVING SUM(NoOfUnits) != 0
)
SELECT startTime
,endTime
,SUM(NoOfUnits)
FROM summaryCTE
group by startTime
,endTime
OPTION (MAXRECURSION 0)

Answer 2

If I understand you correctly, have a look at this example. Please let me know if you have more questions.
DECLARE #Table TABLE(
DateVal DATETIME,
NoOfUnits INT
)
INSERT INTO #Table SELECT '01 Mar 2010 00:30', 0
INSERT INTO #Table SELECT '01 Mar 2010 23:00', 10
INSERT INTO #Table SELECT '01 Mar 2010 23:30', 10
INSERT INTO #Table SELECT '02 Mar 2010 00:30', 10
INSERT INTO #Table SELECT '02 Mar 2010 01:00', 0
INSERT INTO #Table SELECT '02 Mar 2010 02:30', 20
INSERT INTO #Table SELECT '02 Mar 2010 03:30', 30
INSERT INTO #Table SELECT '02 Mar 2010 04:30', 40
INSERT INTO #Table SELECT '02 Mar 2010 05:00', 0
SELECT *
FROM #Table
;WITH DateValues AS(
SELECT t.DateVal,
t.NoOfUnits,
MIN(tNext.DateVal) MinDate
FROM #Table t LEFT JOIN
#Table tNext ON t.DateVal < tNext.DateVal
AND tNext.NoOfUnits = 0
WHERE t.NoOfUnits != 0
GROUP BY t.DateVal,
t.NoOfUnits
)
, DateRanges AS(
SELECT DateVal StartDate,
NoOfUnits,
ISNULL((SELECT MAX(DateVal) FROM #Table WHERE DateVal < MinDate), (SELECT MAX(DateVal) FROM #Table)) EndDateEndDate
FROM DateValues
)
SELECT MIN(StartDate) StartDate,
SUM(NoOfUnits) TotalUnits,
EndDate
FROM DateRanges
GROUP BY EndDate
Ouput
StartDate TotalUnits EndDate
----------------------- ----------- -----------------------
2010-03-01 23:00:00.000 30 2010-03-02 00:30:00.000
2010-03-02 02:30:00.000 90 2010-03-02 04:30:00.000