Add negative and positive number in a column.

Create a table :
 CREATE TABLE HR.T2
(
  VALUE  NUMBER(6)
)

Insert the data : 
SET DEFINE OFF;
Insert into T2 (VALUE) Values
   (2);
Insert into T2
   (VALUE)
 Values
   (3);
Insert into HR.T2
   (VALUE)
 Values
   (4);
Insert into HR.T2
   (VALUE)
 Values
   (-4);
Insert into HR.T2
   (VALUE)
 Values
   (-2);
Insert into HR.T2
   (VALUE)
 Values
   (-1);
Insert into HR.T2
   (VALUE)
 Values
   (1);
COMMIT;

SQL> select * from t2;

     VALUE
----------
         2
         3
         4
        -4
        -2
        -1
         1

7 rows selected.

SQL> select sum(sum (case when value< 0 then value end)) as negative_sum, sum(su
m(case when value>0 then value end)) as positive_sum from t2 group by value;

NEGATIVE_SUM              POSITIVE_SUM
------------                              ------------
          -7                                 10