Overnight Rules Query - sql

Question

I have data:
Current Data
StartDate
StartTime
EndDate
EndTime
12/10/2020
09:00:00
12/13/2020
12:00:00
And I want an output as follows:
Output Data
StartDate
StartTime
EndDate
EndTime
Duration
12/10/2020
09:00:00
12/10/2020
23:59:59
14:59:59
12/11/2020
00:00:00
12/11/2020
23:59:59
23:59:59
12/12/2020
00:00:00
12/12/2020
23:59:59
23:59:59
12/13/2020
00:00:00
12/13/2020
12:00:00
12:00:00
How is it possible in T-SQL? I am running SQL Server 14.x version.
My attempt:
With cte as(
Select [Start Date] StartDate ,
Case
When [Start Date] = [End Date] Then Duration
When [Start Date] != [End Date] Then DateDiff(MINUTE,[Start Time],'23:59:59')
End
as ShutdownTime
from [dbo].[Delay]
where
[Start Date]>=#StartDate and [Start Date]<= #EndDate
Union
Select [End Date] StartDate,
DateDiff(Minute,'00:00:00', [End Time])
as ShutdownTime
from [dbo].[Delay]
where [Start Date] !=[End Date]
and
[Start Date]>=#StartDate and [Start Date]<= #EndDate
)
Select StartDate, Sum(ShutDownTime/cast(60 as float)) ShutDownTime
from cte group by StartDate
If it is less than 24 hrs. it works fine. but in case of more than 24 hrs, it fails.

Answer 1

First, it is much simpler to work with date/times rather than having them in separate columns.
Second, you want a recursive CTE. Here is working code:
with cte as (
select convert(datetime, startdate) + convert(datetime, starttime) as day_startdt,
(case when t.startdate = t.enddate
then v.enddt else dateadd(day, 1, t.startdate)
end) as day_enddt,
v.enddt, 1 as lev
from t cross apply
(values (convert(datetime, enddate) + convert(datetime, endtime))) v(enddt)
union all
select cte.day_enddt,
(case when cte.day_enddt < convert(date, cte.enddt)
then dateadd(day, 1, cte.day_enddt) else cte.enddt
end) as day_enddt,
cte.enddt, lev + 1
from cte
where cte.day_startdt < dateadd(day, -1, cte.enddt)
)
select *
from cte;
Here is a db<>fiddle.
Note that this includes full days, which makes sense to me. It does not calculate the duration, because that calculation does not look correct in the question -- and if it is, you need to explain it.
You can easily split this into separate date/time columns if you want, although I don't recommend doing that.

Answer 2

I recommend to create a View with calculated column:
CREATE VIEW [schema_name.]view_name
AS SELECT
StartDate, StartTime, EndDate, EndTime,
DATEDIFF(hour, StartTime, EndTime) + ':' +
DATEDIFF(minute, StartTime, EndTime) + ':' +
DATEDIFF(second, StartTime, EndTime) + ':' AS 'Duration'
FROM [schema_name.]table_name;
Links:
CREATE VIEW
DATEDIFF
If your date/time isn't of type DATETIME (or similar), have a look at CAST and CONVERT

Answer 3

DECLARE #StartDate DATE = '2020-10-12';
DECLARE #StartTime TIME = '09:00:00';
DECLARE #EndDate DATE = '2020-12-12';
DECLARE #EndTime TIME = '12:00:00';
WITH cte as (
select
#StartDate as StartDate,
#StartTime as StartTime,
CASE WHEN #StartDate<>#EndDate THEN #StartDate ELSE #EndDate END as EndDate,
CASE WHEN #StartDate<>#EndDate THEN CAST('23:59:59' AS TIME) ELSE #EndTime END as EndTime
union all
select
DATEADD(day,1,StartDate),
StartTime,
DATEADD(day,1,EndDate),
CASE WHEN EndDate<>#EndDate THEN CAST('23:59:59' AS TIME) ELSE #EndTime END as EndTime
from cte
where EndDate <= #EndDate
)
select
StartDate,
StartTime,
EndDate,
EndTime,
CONVERT(TIME,DATEADD(second, DATEDIFF(second,StartTime,EndTime),0)) as Duration
from cte;
The duration is calculated as the difference between StartTime and EndTime, because storing values in a database that depend only on other fields (in the same table) is not a smart thing to do.