Query to get cumulative count

For below query we require one more column that will hold cumulative values for salary :
select * from emp ;

NAME       SAL
----------------
lalit            5
sandeep   10
rahul         10
pravin      17

Query :


SELECT b.name,  b.sal, SUM (a.sal) AS cum_sal
    FROM emp a, emp b
   WHERE a.ROWID <= b.ROWID
GROUP BY b.name, b.ROWID, b.sal;

queryoutput

NAME  SAL CUM_SAL
------------------
lalit             5   5
rahul           10  25
pravin         17  42
sandeep       10  15