Query to get MIN hour

Question

Hello to all.
How I can get row having MIN hour(DESPITE DAY) ( for the first six hour 08:00 to 14:00 , AND NEXT 6 hour 14:01 to 20:00 )
if this following is my sample
03/05/2012 17:30:00
04/05/2012 17:00:00
10/05/2012 18:00:00
12/05/2012 08:00:00
10/05/2012 07:00:00 
03/05/2012 11:00:00  my result should be 07:00:00 first six hours, and 17:00:00 next six)
Thanks in advance for any help

Answer 1

It looks like you're talking about 6 hours blocks in the day, offset by 2 hours from midnight, so this should give you some idea of what you could do...
SQL> ed
Wrote file afiedt.buf
  1  with t as (select to_date('03/05/2012 17:30:00','DD/MM/YYYY HH24:MI:SS') as dt from dual union all
  2             select to_date('04/05/2012 17:00:00','DD/MM/YYYY HH24:MI:SS') from dual union all
  3             select to_date('10/05/2012 18:00:00','DD/MM/YYYY HH24:MI:SS') from dual union all
  4             select to_date('12/05/2012 08:00:00','DD/MM/YYYY HH24:MI:SS') from dual union all
  5             select to_date('10/05/2012 07:00:00','DD/MM/YYYY HH24:MI:SS') from dual union all
  6             select to_date('03/05/2012 11:00:00','DD/MM/YYYY HH24:MI:SS') from dual
  7            )
  8  --
  9  -- end of example data
10  --
11  select case dt_part
12           when 1 then '02:00:00 to 07:59:59'
13           when 2 then '08:00:00 to 13:59:59'
14           when 3 then '14:00:00 to 19:59:59'
15           when 4 then '20:00:00 to 01:59:59'
16         else null end as tm_part
17        ,to_char(min(to_date(to_char(dt,'HH24:MI:SS'),'HH24:MI:SS')),'HH24:MI:SS') as min_tm
18  from (
19        select dt
20              ,case when offset_dt between to_date('00','HH24') and to_date('05:59:59','HH24:MI:SS') then 1
21                    when offset_dt between to_date('06','HH24') and to_date('11:59:59','HH24:MI:SS') then 2
22                    when offset_dt between to_date('12','HH24') and to_date('17:59:59','HH24:MI:SS') then 3
23                    when offset_dt between to_date('18','HH24') and to_date('23:59:59','HH24:MI:SS') then 4
24               else null end as dt_part
25        from (
26              select dt, to_date(to_char(dt-(2/24),'HH24:MI:SS'),'HH24:MI:SS') offset_dt
27              from t
28             )
29       )
30  group by dt_part
31* order by dt_part
SQL> /
TM_PART              MIN_TM
02:00:00 to 07:59:59 07:00:00
08:00:00 to 13:59:59 08:00:00
14:00:00 to 19:59:59 17:00:00The conversions between date and char take place to remove the date component and thus normalise all the times to be on the same day.
Edited by: BluShadow on 16-Nov-2012 15:10
Note, in the above solution the times that fall between 20:00:00 and 01:59:59 will treat the times from 00:00:00 to 01:59:59 as being before 20:00:00 so such times will come out as the minimum. If it's the ealiest time in that block of 6 hours you want, then a little more coding is required to get the minimum based on the offset time. But I'm not going to code that, as it's still not exactly clear what the issue is that is trying to be solved.