Counting minutes between two times for a daterange - sql

Question

Using SQL Server 2008 I would like to count the amount of minutes that land between 16:30 and 18:00 for a given date range.
So inputs are for example #fromdate = '2017-04-17 17:00:00' and #todate = '2017-04-19 17:00:00'
So for the above example using lamens maths.
Day 1 (17th) : 60
Day 2 (18th) : 90
Day 3 (19th) : 30
Total 180
Day 1 is 60 because there is 60 minutes between the start date 17:00 and 18:00 Day 2 is 90 because the middle date must be the full 90 minutes between 16:30 and 18:00 Day 3 is 30 because there is 30 minutes between 16:30 and 17:00 (the time of the end date) So I am searching for the ammount of minutes between 16:30 and 18:00 for each day if that makes sense.
I would like the total to be the output.

Answer 1

This will work in sql server. We populate our start and end datetimes in a cte. After that, it is as simple as summing the date difference in minutes:
declare #fromdate datetime = convert(datetime,'2017-04-17 17:00:00',20)
declare #todate datetime = convert(datetime,'2017-04-19 17:00:00',20)
declare #startRangeTime time = '16:30';
declare #endRangeTime time = '18:00';
with dates as (
select top (datediff(day, #fromdate, #toDate) + 1)
case when dateadd(day,row_number() over (order by a.object_id) - 1, cast(#fromdate as date)) = cast(#fromdate as date)
then #fromdate
else cast(dateadd(day,row_number() over (order by a.object_id) - 1, cast(#fromdate as date)) as datetime) + cast(#startRangeTime as datetime)
end as startDt,
case when dateadd(day,row_number() over (order by a.object_id) - 1, cast(#fromdate as date)) = cast(#todate as date)
then #todate
else cast(dateadd(day,row_number() over (order by a.object_id) - 1, cast(#fromdate as date)) as datetime) + cast(#endRangeTime as datetime)
end as endDt
from sys.all_objects a
cross join sys.all_objects b
)
select sum(datediff(mi, startDt, endDt)) from dates
returns:
180
generating dates without a loop taken from this series on generating a sequence without loops

Answer 2

You cannot subtract 2 strings so do it this way. The sample code to get the time in minutes between 2 dates.
ALTER SESSION SET NLS_LANGUAGE="American"
WITH source as (
SELECT '30-OCT-2016 21:08:34' as A, '30/10/2016 21:06:34' as B
FROM Dual
)
SELECT TO_DATE(A, 'DD-MON-YYYY HH24:MI:SS') as new_a,
TO_DATE(B, 'DD/MM/YYYY HH24:MI:SS') as new_b,
( TO_DATE(A, 'DD-MON-YYYY HH24:MI:SS')
- TO_DATE(B, 'DD/MM/YYYY HH24:MI:SS')
) * 24 * 60 as result
FROM source
Hope this helps...