AVG

AVG([ DISTINCT  ALL ] expr) OVER(analytic_clause) 

obclient> CREATE TABLE EXPLOYEES(LAST_NAME CHAR(10), SALARY DECIMAL, JOB_ID CHAR(32));
Query OK, 0 rows affected (0.08 sec)

obclient> INSERT INTO EXPLOYEES VALUES('JIM', 2000, 'CLEANER');
Query OK, 1 row affected (0.11 sec)

obclient> INSERT INTO EXPLOYEES VALUES('MIKE', 12000, 'ENGINEERING');
Query OK, 1 row affected (0.00 sec)

obclient> INSERT INTO EXPLOYEES VALUES('LILY', 13000, 'ENGINEERING');
Query OK, 1 row affected (0.00 sec)

obclient> INSERT INTO EXPLOYEES VALUES('TOM', 11000, 'ENGINEERING');
Query OK, 1 row affected (0.01 sec)

obclient> SELECT LAST_NAME, AVG(SALARY) OVER(PARTITION BY JOB_ID) AVG_S FROM EXPLOYEES;
+-----------+------------+
 LAST_NAME  AVG_S      
+-----------+------------+
 JIM         2000.0000 
 MIKE       12000.0000 
 LILY       12000.0000 
 TOM        12000.0000 
+-----------+------------+
4 rows in set (0.01 sec)