How to get the count for every 30 mins

Question

Hi,
Following is the table format:
Time ******************** logged in users
9/5/2006 8:38:22 PM**** 2
9/5/2006 8:38:44 PM**** 4
9/5/2006 8:40:22 PM**** 1
9/5/2006 8:41:22 PM**** 3
9/5/2006 8:52:22 PM**** 6
9/5/2006 9:02:22 PM**** 5
9/5/2006 9:04:24 PM**** 3
9/5/2006 9:08:26 PM**** 4
9/5/2006 9:10:28 PM**** 6
What I need is number of users logged in for every 30 min
like 9/5/2006 9:00:00(8:30 to 9:00) is 16
9/5/2006 9:30:00(9:00 to 9:30) is 18
Can any one help me in this regard?
-Raj

Answer 1

The trick is to group your times to every 30 min.
Unfortunatly there is no way to TRUNC(30 min).
But you can build this function yourself using some mathematical logic and trunc to build the groups.
Look at this code piece:
select trunc(sysdate) + trunc((sysdate - trunc(sysdate))*24*2)/24/2
from dualInstead of sysdate use your date column and group by the expression.
Added example using Dave's test data
WITH t AS
        SELECT TO_DATE ('9/5/2006 8:38:22 PM', 'fmdd/mm/yyyy hh:mi:ss pm') tm,
               2 num
          FROM DUAL
        UNION
        SELECT TO_DATE ('9/5/2006 8:38:44 PM', 'fmdd/mm/yyyy hh:mi:ss pm') tm,
               4 num
          FROM DUAL
        UNION
        SELECT TO_DATE ('9/5/2006 8:40:22 PM', 'fmdd/mm/yyyy hh:mi:ss pm') tm,
               1 num
          FROM DUAL
        UNION
        SELECT TO_DATE ('9/5/2006 8:41:22 PM', 'fmdd/mm/yyyy hh:mi:ss pm') tm,
               3 num
          FROM DUAL
        UNION
        SELECT TO_DATE ('9/5/2006 8:52:22 PM', 'fmdd/mm/yyyy hh:mi:ss pm') tm,
               6 num
          FROM DUAL
        UNION
        SELECT TO_DATE ('9/5/2006 9:02:22 PM', 'fmdd/mm/yyyy hh:mi:ss pm') tm,
               5 num
          FROM DUAL
        UNION
        SELECT TO_DATE ('9/5/2006 9:04:24 PM', 'fmdd/mm/yyyy hh:mi:ss pm') tm,
               3 num
          FROM DUAL
        UNION
        SELECT TO_DATE ('9/5/2006 9:08:26 PM', 'fmdd/mm/yyyy hh:mi:ss pm') tm,
               4 num
          FROM DUAL
        UNION
        SELECT TO_DATE ('9/5/2006 9:10:28 PM', 'fmdd/mm/yyyy hh:mi:ss pm') tm,
               6 num
          FROM DUAL)
SELECT   SUM (num), trunc(tm) + trunc((tm - trunc(tm))*24*2)/24/2 halfhours
    FROM t
GROUP BY trunc(tm) + trunc((tm - trunc(tm))*24*2)/24/2;
Row#     SUM(NUM)     HALFHOURS
1     16     09.05.2006 20:30:00
2     18     09.05.2006 21:00:00Message was edited by:
Sven Weller