Problem getting accumulative value by a user defined week

Question

I have a requirement where I have to accumulative values by week where a week is defined as Sunday to Saturday. For example:
date           value     acc_value          
9/1/2010     2     2          Wed     
9/2/2010     5     7          Thur     
9/3/2010     3     10          Fri     
9/4/2010     4     14          Sat     
9/5/2010     8     8          Sun     value is reset
9/6/2010     2     10          Mon     
9/7/2010     1     11         Tue     
9/8/2010     4     15         Wed     
9/9/2010     7     22         Thu     
9/10/2010     4     26          Fri     
9/11/2010     5     31         Sat     Any help would be appreciated.
Thanks.

Answer 1

Try this:
with my_table as (select to_date('01/09/2010', 'dd/mm/yyyy') dt, 2 value from dual union all
                  select to_date('02/09/2010', 'dd/mm/yyyy') dt, 5 value from dual union all
                  select to_date('03/09/2010', 'dd/mm/yyyy') dt, 3 value from dual union all
                  select to_date('04/09/2010', 'dd/mm/yyyy') dt, 4 value from dual union all
                  select to_date('05/09/2010', 'dd/mm/yyyy') dt, 8 value from dual union all
                  select to_date('06/09/2010', 'dd/mm/yyyy') dt, 2 value from dual union all
                  select to_date('07/09/2010', 'dd/mm/yyyy') dt, 1 value from dual union all
                  select to_date('08/09/2010', 'dd/mm/yyyy') dt, 4 value from dual union all
                  select to_date('09/09/2010', 'dd/mm/yyyy') dt, 7 value from dual union all
                  select to_date('10/09/2010', 'dd/mm/yyyy') dt, 4 value from dual union all
                  select to_date('11/09/2010', 'dd/mm/yyyy') dt, 5 value from dual)
-- end of mimicking your data in a table called my_table
select dt,
       value,
       sum(value) over (partition by trunc(dt+1, 'iw') order by dt) acc_value,
       to_char(dt, 'dy') dy
from   my_table
order by dt;
DT              VALUE  ACC_VALUE DY
01/09/2010          2          2 wed
02/09/2010          5          7 thu
03/09/2010          3         10 fri
04/09/2010          4         14 sat
05/09/2010          8          8 sun
06/09/2010          2         10 mon
07/09/2010          1         11 tue
08/09/2010          4         15 wed
09/09/2010          7         22 thu
10/09/2010          4         26 fri
11/09/2010          5         31 sat