How to count transactions by mutiple days (group by two days)

Question

Hi,
I am looking for a SQL solution which provides count of transactions by two days / three days etc. (e.g. GROUP BY two days).
I tried the following approach
select
id
, counT(*) OVER (PARTITION BY trunc(date_field) + INTERVAL '1' DAY)
from tablename
However this would give me count for each row in the table. I am looking for a solution, which provides me one row for each two days interval
Appreciate your help..

Answer 1

Hi,
If you want to collapse the results down to one row per unique value of day_breaker (and, depending on your requirements, id) then use the aggregate SUM function; it's simpler than the analytic SUM.
MIN (day_breaker) may not be the first day of the period. For example, if you add this row to your sample data:
insert into TEST_X (id, trans_id, date_field)
     values     (1,  6,        TO_DATE('01/06/2012','mm/dd/yyyy'))
/then the output will contain these day_breakers:
1/1/2012
1/3/2012
1/6/2012          (not 1/5/2012)Try this:
WITH     got_day_breaker     AS
     SELECT     id, trans_id
     ,     date_field          -- For debugging only
     ,     DATE '2012-01-01' + ( 2 * FLOOR ( (date_field - DATE '2012-01-01')
                              / 2
                        )     AS day_breaker
     FROM     test_x
SELECT       id
,       day_breaker
,       COUNT (*)     AS cnt
FROM       got_day_breaker
GROUP BY  id
,       day_breaker
ORDER BY  id
,       day_breaker
;