Modifying a View

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);

SQL> CREATE OR REPLACE VIEW emp_view AS
  2  SELECT AVG(sal) average_salary
  3  FROM emp
  4  GROUP BY deptno;

View created.

SQL>