How to add Cumulative Total Oracle Query

 SELECT * FROM EMP;

 SELECT EMPNO
      ,ENAME
      ,dept_no
      ,SAL
      ,SUM(sal) over(ORDER BY empno) AS dept_cum
  FROM EMP
 ORDER BY empno;

Lets group the Cumulative Sum Based on DepartmentId

SELECT EMPNO
      ,ENAME
      ,dept_no
      ,SAL
      ,SUM(sal) over(PARTITION BY dept_no ORDER BY empno) AS dept_cum
  FROM EMP
 ORDER BY empno;