"Balance forward" SQL statement

Question

Has anyone developed a SQL statement that allows balances to be carried forward? Would a UNION query possibly work?
Here's my example where I need to join 3 tables and show results. Based on the example data below, I am looking for a query that allows me to illustrate that the Acrobat 9 Installed Software instances are consuming a license capacity of 6, leaving a balance of 4 that can be applied to the Acrobat 8 Installed Software Instances.
Table: LICENSE
LICENSENUM     SWLICENSE          LICENSECAPACITY
'1001'          'Adobe Acrobat 9'     '10'
Table: LICENSESW
LICENSENUM     SWPRODUCT     PRECEDENCE
'1001'     'Acrobat 9'     '1'
'1001'     'Acrobat 8'     '2'
Table: INSTALLEDSW
INSTALLEDSW
'Acrobat 9'
'Acrobat 9'
'Acrobat 9'
'Acrobat 9'
'Acrobat 9'
'Acrobat 9'
'Acrobat 8'
'Acrobat 8'
'Acrobat 8'
'Acrobat 8'
'Acrobat 8'
I can write a select to do total counts, but this does not allow me to carry a balance forward to be applied to Acrobat 8 (precedence 2).
select LICENSE.SWLICENSE, LICENSE.LICENSECAPACITY, count(INSTALLEDSW.INSTALLEDSW) as INSTALLED_COUNT
from LICENSE, LICENSESW, INSTALLEDSW
where LICENSE.LICENSENUM = LICENSESW.LICENSENUM
AND LICENSESW.SWPRODUCT = INSTALLEDSW.INSTALLEDSW
group by LICENSE.SWLICENSE, LICENSE.LICENSECAPACITY;
Results:
SWLICENSE          LICENSECAPACITY          INSTALLED_COUNT
'Adobe Acrobat 9'     '10'               '11'
I need results that look like this, where the balance of 4 is carried forward after the first row:
SWLICENSE          LICENSECAPACITY          INSTALLED_PRODUCT     INSTALLED_COUNT
'Adobe Acrobat 9'     '6'               'Acrobat 9'          '6'
'Adobe Acrobat 9'     '4'               'Acrobat 8'          '5'

Answer 1

Not easy to follow your example data, but if I demonstrate what I think you are trying to achieve using the emp table, you may be able to see if it helps...
SQL> select deptno, empno, ename
  2        ,count(*) over (partition by deptno) as dept_count
  3        ,count(*) over (partition by deptno) - row_number() over (partition by deptno order by empno) as remaining
  4  from   emp
  5  order by deptno, empno;
    DEPTNO      EMPNO ENAME      DEPT_COUNT  REMAINING
        10       7782 CLARK               3          2
        10       7839 KING                3          1
        10       7934 MILLER              3          0
        20       7369 SMITH               5          4
        20       7566 JONES               5          3
        20       7788 SCOTT               5          2
        20       7876 ADAMS               5          1
        20       7902 FORD                5          0
        30       7499 ALLEN               6          5
        30       7521 WARD                6          4
        30       7654 MARTIN              6          3
        30       7698 BLAKE               6          2
        30       7844 TURNER              6          1
        30       7900 JAMES               6          0
14 rows selected.using the analytical functions count() and row_number() (you can use others such as sum(), avg(), lag(), lead() etc. as required) you can do processing that carries forward, backwards or across "groups" (aka partitions) of data.