Hy this is what my script looks like:

set sqlmathmode round
select count(*) as "process", -
case -
when sum(bytes) > 1073741824 then -
cast(sum(bytes)/1073741824 as varchar(24))||'Gb' -
when sum(bytes) > 1048576 then -
cast(sum(bytes)/1048576 as varchar(24))||'Mb' -
when sum(bytes) > 1024 then -
cast(sum(bytes)/1024 as varchar(24))||'Kb' -
else cast(sum(bytes) as varchar(24)) -
end as "Num Bytes", -
activity as "(17h till 17h)act." - 
from summary -
where (date(start_time) = current date - 1 day -
and time(start_time) > '17:00') -
or -
(date(start_time) = current date -
and time(start_time) < '17:00') - 
group by activity

any ideas yet?