How to group by hour in HANA - sql

Question

I have the following table in HANA :
vehicle_id time roaming_time parking_time
1 Sep 01,2016 3:09:03 AM 3 9
2 Sep 01,2016 3:12:03 AM 6 8
1 Sep 01,2016 9:10:03 AM 10 6
4 Sep 01,2016 10:09:03 AM 9 3
1 Sep 01,2016 10:10:03 AM 10 10
4 Sep 01,2016 12:09:03 AM 3 9
from these information I wanted to know that what is the sum of roaming_time and sum of parking_time for each hour from all the vehicles and want the output in the format:
time roaming_time parking_time
____ _____________ ____________
2016-09-01 00:00:00 3 9
2016-09-01 01:00:00 6 8
2016-09-01 02:00:00 9 6
2016-09-01 03:00:00 3 6
2016-09-01 04:00:00 12 3
2016-09-01 05:00:00 15 8
2016-09-01 06:00:00 18 4
2016-09-01 07:00:00 8 3
2016-09-01 08:00:00 9 4
2016-09-01 09:00:00 6 6
2016-09-01 10:00:00 6 9
........
2016-09-01 23:00:00 3 12
I need to group the following query which gives all the sum by hour wise and get the expected result:
select sum(roaming_time) as roaming_time,sum(parking_time) as parking_time
from time>='2016-09-01 00:00:00'
time>='2016-09-01 23:59:59'
I do not know how to do the grouping by hour in HANA. Any help is appreciated

Answer 1

Here is one method . . . it converts the time to a date and hour format:
select to_varchar(time, 'YYYY-MM-DD'), hour(time),
sum(roaming_time) as roaming_time, sum(parking_time) as parking_time from t
group by date(time), hour(time)
order by to_varchar(time, 'YYYY-MM-DD'), hour(time);

Answer 2

Use a group by clause with SERIES_ROUND(). Avoid date() and hour() and similar data/time functions on large data sets as they tend to be slower.
select SERIES_ROUND(time, 'INTERVAL 1 HOUR') as time,
sum(roaming_time) as roaming_time, sum(parking_time) as parking_time from t
group by SERIES_ROUND(time, 'INTERVAL 1 HOUR')
order by SERIES_ROUND(time, 'INTERVAL 1 HOUR');

Answer 3

Another approach is to convert it to a string, especially if no further time calculations are required.
This could look like this:
select to_varchar(time, 'DD.MM.YYYY HH24') as parking_hour ,
sum(roaming_time) as roaming_time, sum(parking_time) as parking_time from t
group by to_varchar(time, 'DD.MM.YYYY HH24') as parking_hour
order byto_varchar(time, 'DD.MM.YYYY HH24') as parking_hour;