Our test database samples:


SQL> desc test_sum1;
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------
 DB                                                 NUMBER(5)
 CR                                                 NUMBER(5)
 OPB                                                NUMBER(5)

SQL> select * from test_sum1;

        DB         CR        OPB
---------- ---------- ----------
         0          0       1000
         0        500
         0        300
       -200          0
      - 100          0
      - 700          0

6 rows selected.

Opb?open balance ,cr-? credit, db? debit

Debit (minus)
Credit (plus)

But needed result:
-------------------
1000      (1000+0+0)
1500      (1000+0+500)
1800      (1500+0+300)
1600      (1800-200+0)
1500      (1600-100+0)
800        (1500-700+0)