Analytical Functions Oracle PLSQL

SQL> CREATE TABLE employee(
  2    employee_id INTEGER,
  3    division_id CHAR(3),
  4    job_id CHAR(3),
  5    first_name VARCHAR2(10) NOT NULL,
  6    last_name VARCHAR2(10) NOT NULL,
  7    salary NUMBER(6, 0)
  8  );
Table created.
SQL>
SQL> insert into employee (EMPLOYEE_ID,division_id,JOB_ID,FIRST_NAME,LAST_NAME,SALARY)
  2                 values(1, 'BUS','PRE','James','Smith','800000');
1 row created.
SQL> insert into employee (EMPLOYEE_ID,division_id,JOB_ID,FIRST_NAME,LAST_NAME,SALARY)
  2                 values(2, 'SAL','MGR','Ron','Johnson','350000');
1 row created.
SQL> insert into employee (EMPLOYEE_ID,division_id,JOB_ID,FIRST_NAME,LAST_NAME,SALARY)
  2                 values(3, 'SAL','WOR','Fred','Hobbs','140000');
1 row created.
SQL> insert into employee (EMPLOYEE_ID,division_id,JOB_ID,FIRST_NAME,LAST_NAME,SALARY)
  2                 values(4, 'SUP','MGR','Susan','Jones','200000');
1 row created.
SQL> insert into employee (EMPLOYEE_ID,division_id,JOB_ID,FIRST_NAME,LAST_NAME,SALARY)
  2                 values(5, 'SAL','WOR','Rob','Green','350000');
1 row created.
SQL>
SQL> select * from employee;
EMPLOYEE_ID DIV JOB FIRST_NAME LAST_NAME      SALARY
----------- --- --- ---------- ---------- ----------
          1 BUS PRE James      Smith          800000
          2 SAL MGR Ron        Johnson        350000
          3 SAL WOR Fred       Hobbs          140000
          4 SUP MGR Susan      Jones          200000
          5 SAL WOR Rob        Green          350000
SQL>
SQL>
SQL> --Eliminate duplicate rows using a HAVING clause that only allows rows whose 
GROUP_ID() is 0
SQL>
SQL> SELECT division_id, job_id, GROUP_ID(), SUM(salary)
  2  FROM employee
  3  GROUP BY division_id, ROLLUP(division_id, job_id)
  4  HAVING GROUP_ID() = 0;
DIV JOB GROUP_ID() SUM(SALARY)
--- --- ---------- -----------
BUS PRE          0      800000
SAL MGR          0      350000
SAL WOR          0      490000
SUP MGR          0      200000
BUS              0      800000
SAL              0      840000
SUP              0      200000
7 rows selected.
SQL>
SQL>
SQL>
SQL> drop table employee;
Table dropped.
SQL>