# Cumulative Sum

You can perform window function with the following functions: ```SUM(), AVG(), MAX(), MIN(), COUNT(), VARIANCE(), and STDDEV()```.

The following query performs a cumulative sum to compute the cumulative salaries amount, starting with each department.

`SUM(amount)` computes the sum of an amount. The outer `SUM()` computes the cumulative amount. `ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW` defines the start and end of the window. The start is set to `UNBOUNDED PRECEDING`. `UNBOUNDED PRECEDING` means that the start of the window is fixed at the first row in the result set. `CURRENT ROW` sets the end of the window. `CURRENT ROW` represents the current row in the result set.

``````
CREATE TABLE EMP (EMPNO NUMBER(4) NOT NULL,
ENAME VARCHAR2(10),
JOB VARCHAR2(9),
SAL NUMBER(7, 2),
DEPTNO NUMBER(2));

INSERT INTO EMP VALUES (1, 'SMITH', 'CLERK',     800,    20);
INSERT INTO EMP VALUES (2, 'ALLEN', 'SALESMAN', 1600,    30);
INSERT INTO EMP VALUES (3, 'WARD',  'SALESMAN', 1250,    30);
INSERT INTO EMP VALUES (4, 'JONES', 'MANAGER',  2975,    20);
INSERT INTO EMP VALUES (5, 'MARTIN','SALESMAN', 1250,    30);
INSERT INTO EMP VALUES (6, 'BLAKE', 'MANAGER',  2850,    30);
INSERT INTO EMP VALUES (7, 'CLARK', 'MANAGER',  2850,    10);
INSERT INTO EMP VALUES (8, 'SCOTT', 'ANALYST',  3000,    20);
INSERT INTO EMP VALUES (9, 'KING',  'PRESIDENT',3000,    10);
INSERT INTO EMP VALUES (10,'TURNER','SALESMAN', 1500,    30);
INSERT INTO EMP VALUES (11,'ADAMS', 'CLERK',    1500,    20);

SQL> SELECT deptno, SUM(sal) AS dept_salary,
2  SUM(SUM(sal)) OVER (ORDER BY deptno ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW)
3  AS cumulative_amount
4  FROM emp
5  GROUP BY deptno
6  ORDER BY deptno;

DEPTNO DEPT_SALARY CUMULATIVE_AMOUNT
---------- ----------- -----------------
10        5850              5850
20        8275             14125
30        8450             22575

SQL>
``````

The following query uses a cumulative sum to compute the cumulative salary amount, starting with employee number 2 to 6:

``````
SQL> SELECT deptno, SUM(sal) AS month_amount,
2  SUM(SUM(sal)) OVER
3  (ORDER BY deptno ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) AS
4  cumulative_amount
5  FROM emp
6  WHERE empno  BETWEEN 2 AND 6
7  GROUP BY deptno
8  ORDER BY deptno;

DEPTNO MONTH_AMOUNT CUMULATIVE_AMOUNT
---------- ------------ -----------------
20         2975              2975
30         6950              9925

SQL>
``````
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Window Functions:
1. Cumulative Sum
2. Moving Average
3. Centered Average
4. FIRST_VALUE()
5. LAST_VALUE
Related: