# Centered Average

The following query computes the moving average of the salary amount centered between the previous and next department from the current department: `ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING` defines the start of the window as including the row preceding the current row being processed. The end of the window is the row following the current row.

``````
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_amount,
2  AVG(SUM(sal)) OVER (ORDER BY deptno ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING)
3  AS moving_average
4  FROM emp
5  GROUP BY deptno
6  ORDER BY deptno;

DEPTNO DEPT_AMOUNT MOVING_AVERAGE
---------- ----------- --------------
10        5850         7062.5
20        8275           7525
30        8450         8362.5

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