Formula implementation issue

Question

I have facing a problem to implement below issue.
below is the example
Master table          
code     desc     
1     REVENUES     
2     CAPITAL CHARGE     
3     REVENUES / Capital charge., %     
Transaction table          
code     process month     Amount
1     30-Apr-11     100
2     1-May-11     5000
we have to calculate value for code 3 like (code 1 /code 2)*100          
I want we want to keep this formula in a table and calculate as per formula given in the table ( formula is changeable) and because of this we can't write any direct formula in the procedure.
I am seeking help from forum on this issue. Thanks in advance.

Answer 1

Your solution needs small adjustement. You shoud generate xml not for whole table but just for the current row:
SQL> select * from t
  2  /
  REVENUES CAPITAL_CHARGE EQUATION
        10            100 REVENUES / CAPITAL_CHARGE
        20             50 REVENUES / CAPITAL_CHARGE
SQL> SELECT                                                     
  2                   REVENUES, CAPITAL_CHARGE,
  3                    TO_NUMBER (
  4                       EXTRACTVALUE (
  5                          xmltype (
  6                             DBMS_XMLGEN.
  7                              getxml ( 'SELECT '||EQUATION ||' RESULT FROM T'
  8                                )),
  9                          '/ROWSET/ROW/RESULT'))
10                       result
11               FROM t
12  /
                        xmltype (
ERROR at line 5:
ORA-19025: EXTRACTVALUE returns value of only one node
SQL > SELECT
                  REVENUES, CAPITAL_CHARGE,
                   TO_NUMBER (
                      EXTRACTVALUE (
                         xmltype (
                            DBMS_XMLGEN.
                             getxml ( 'SELECT '||EQUATION ||' RESULT FROM T WHERE ROWID = ''' || ROWID || ''''
                         '/ROWSET/ROW/RESULT'))
                      result
              FROM t
  REVENUES CAPITAL_CHARGE     RESULT
        10            100         .1
        20             50         .4
SQL> SY.