how to sum total hours from date-time field in sql

I am trying to sum total hours that someone was sleeping from date-time field.  For example,  if a person sleeps at 1:00 am and wakes up on 5:00 am then i want to show that person slept for 4 hours as total hours of sleep from 1 to 5 am.  I want to extract the hour and the minutes from the date-field.  Here is how it look like my date-field
2015-02-19 00:00:00.000
2015-02-19 00:30:00.000
2015-02-19 01:00:00.000
2015-02-19 01:30:00.000
2015-02-19 02:00:00.000
2015-02-19 02:30:00.000
2015-02-19 03:00:00.000

Open in new window

This is from 12:00 AM to 3:00 AM so i would expect the total to be 3 Hours.  
I tried this but not working..
select  datepart(hour, cast(FullDatetime as time)) as totHours
from myTable
where id in (1, 2, 3,4,5, 7)

Open in new window

moe57Asked:
Who is Participating?
 
Jim HornConnect With a Mentor Microsoft SQL Server Developer, Architect, and AuthorCommented:
To return hours, with the decimal places to make sure 2.75 doesn't get cut off to 2 ...
SELECT DATEDIFF(minute, Min(tm), Max(tm)) / 60.0 as hours
FROM #tmp

Open in new window

0
 
Jim HornMicrosoft SQL Server Developer, Architect, and AuthorCommented:
Really not following this, but if you're asking for a way to calculate the difference in times between the min and max of a given set, then copy-paste the below into your SSMS, execute to verify it works, then modify to meet your needs
CREATE TABLE #tmp (tm datetime) 

INSERT INTO #tmp (tm) 
VALUES 
('2015-02-19 00:00:00.000'), 
('2015-02-19 00:30:00.000'), 
('2015-02-19 01:00:00.000'), 
('2015-02-19 01:30:00.000'), 
('2015-02-19 02:00:00.000'), 
('2015-02-19 02:30:00.000'), 
('2015-02-19 03:00:00.000')

SELECT DATEDIFF(minute, Min(tm), Max(tm))
FROM #tmp
-- WHERE <whatever>

Open in new window

0
 
moe57Author Commented:
Jim,  i have not looked at  your example yet but all what i need is somehow to sum total hours from the example i mentioned above.  The field has date and time so all what i need is to add up all the times and get the total number of hours which in this case is 3 hours.  I hope i am little bit clearer now.  thanks
0
What Kind of Coding Program is Right for You?

There are many ways to learn to code these days. From coding bootcamps like Flatiron School to online courses to totally free beginner resources. The best way to learn to code depends on many factors, but the most important one is you. See what course is best for you.

 
Jim HornMicrosoft SQL Server Developer, Architect, and AuthorCommented:
Define for us at a Barney level of simplicity how the above set of datetime values adds up to three hours.
0
 
moe57Author Commented:
okay, i am happy to do that..
('2015-02-19 00:00:00.000'),  = 12:00 AM
('2015-02-19 00:30:00.000'),  = 12:30 AM
('2015-02-19 01:00:00.000'),  = 1:00 AM
('2015-02-19 01:30:00.000'),  = 1:30 AM
('2015-02-19 02:00:00.000'),  = 2:00 AM
('2015-02-19 02:30:00.000'),  = 2:30 AM
('2015-02-19 03:00:00.000')  =  3:00 AM
So when you add up from 12:00 am to 3:00 Am  total hours = 3 hours.  I am using military hours.  Thanks
0
 
Jim HornMicrosoft SQL Server Developer, Architect, and AuthorCommented:
That was provided to you in my first comment, where it takes the difference between the minimum and maximum values, then does a DATEDIFF to convert to minutes.  The second comments converts to hours with a decimal value.

If that's not what you need, explain again how the calculation is supposed to work.
0
 
Jim HornMicrosoft SQL Server Developer, Architect, and AuthorCommented:
I think where we may be tripping up here is the use of 'sum up', which implies summing all rows, i.e. midnight + 12:30 + 1 + 1:30 + 2 + 2:30 + 3 would equal 10:30.

I interpreted your question as the maximum value minus the minimum value.

If your definition of 'sum up' is different from the above two, spell it out in more clear language.
0
 
moe57Author Commented:
Jim, thanks for your help.  You did answer my question i just did not see your second answer where you were dividing 60.  Thanks
0
 
moe57Author Commented:
thanks
0
Question has a verified solution.

Are you are experiencing a similar issue? Get a personalized answer when you ask a related question.

Have a better answer? Share it in a comment.

All Courses

From novice to tech pro — start learning today.