Question

I need to create a query to sum day’s hours and night’s hours from a range intersec.
For example with this range:

8AM-8PM -> day
8PM-8AM -> night

and one or more start-end time period:

7.30AM 10.00PM

I would like to get this values:

12 day's hours
2.5 night's hours

I don’t know which is the bast way to accomplish this function.

Answer 1

As i wrote in my comment, it is a brain teaser. I hope you can combine this with your code.

declare @t table(datefrom smalldatetime, dateto smalldatetime)
insert @t values('2012-01-01 10:30', '2012-01-02 09:00')
insert @t values('2012-01-01 08:00', '2012-01-02 20:20')
insert @t values('2012-01-01 19:00', '2012-01-02 13:00')
insert @t values('2012-01-01 20:00', '2012-01-02 00:00')
insert @t values('2012-01-01 23:00', '2012-01-03 00:00')

select datefrom, dateto, day, cast(datediff(minute, datefrom, dateto)/60.0 - day as decimal(9,2)) night
from @t t
cross apply
(select dateadd(day, datediff(hour, '1900-01-01 20:00', datefrom)/24, '1900-01-02 08:00') a,
dateadd(day, datediff(hour, '1901-01-01 09:00', dateto)/24, '1901-01-01 20:00' ) b) c
cross apply 
(select cast(((datediff(hour, a, b) - 12 * datediff(day, a,b)) * 60
+case when a < datefrom then -datediff(minute, a, datefrom) else 0 end
+case when b > dateto then +datediff(minute, b, dateto) else 0 end) / 60.0 as decimal(9,2)) day) e

Result:

datefrom          dateto               day    night
2012-01-01 10:30  2012-01-02 09:00:00  10.50  12.00
2012-01-01 08:00  2012-01-02 20:20:00  24.00  12.33
2012-01-01 19:00  2012-01-02 13:00:00   6.00  12.00
2012-01-01 20:00  2012-01-02 00:00:00   0.00   4.00
2012-01-01 23:00  2012-01-03 00:00:00  12.00  13.00