How can we write this in analytical function..

Question

select a.employee_id,a.last_name,b.count from employees a, (select manager_id, count(manager_id) as count from employees group by manager_id) b where a.employee_id=b.manager_id;
As per my requirement I need each manager name and no of employees reporting to him... above query works.. Could anybody help to write the same using analytic function.... Hw this same can be written in effiect way??? (quick performance)
Please also share the link to download some doc to have good understanding of analytical function..
Thanks in advance....

Answer 1

are you trying to do a hierarchical type of query?
select ename, count(ename) -1 numr_of_emps_under_this_mgr  from  emp
connect by  empno =prior mgr
group by ename
order by count(ename) desc ;
ENAME     NUMR_OF_EMPS_UNDER_THIS_MGR
KING     13
BLAKE     5
JONES     4
CLARK     1
FORD     1
SCOTT     1
ADAMS     0
TURNER     0
MARTIN     0
JAMES     0
SMITH     0
MILLER     0
ALLEN     0
WARD     0Here is the table structure I used (I think you can download it from oracle somewhere)
CREATE TABLE EMP
  EMPNO     NUMBER(4)                           NOT NULL,
  ENAME     VARCHAR2(10 BYTE),
  JOB       VARCHAR2(9 BYTE),
  MGR       NUMBER(4),
  HIREDATE  DATE,
  SAL       NUMBER(7,2),
  COMM      NUMBER(7,2),
  DEPTNO    NUMBER(2)
SET DEFINE OFF;
Insert into EMP
   (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, DEPTNO)
Values
   (7369, 'SMITH', 'CLERK', 7902, TO_DATE('12/17/1980 00:00:00', 'MM/DD/YYYY HH24:MI:SS'),
    800, 20);
Insert into EMP
   (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO)
Values
   (7499, 'ALLEN', 'SALESMAN', 7698, TO_DATE('02/20/1981 00:00:00', 'MM/DD/YYYY HH24:MI:SS'),
    1600, 300, 30);
Insert into EMP
   (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO)
Values
   (7521, 'WARD', 'SALESMAN', 7698, TO_DATE('02/22/1981 00:00:00', 'MM/DD/YYYY HH24:MI:SS'),
    1250, 500, 30);
Insert into EMP
   (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, DEPTNO)
Values
   (7566, 'JONES', 'MANAGER', 7839, TO_DATE('04/02/1981 00:00:00', 'MM/DD/YYYY HH24:MI:SS'),
    2975, 20);
Insert into EMP
   (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO)
Values
   (7654, 'MARTIN', 'SALESMAN', 7698, TO_DATE('09/28/1981 00:00:00', 'MM/DD/YYYY HH24:MI:SS'),
    1250, 1400, 30);
Insert into EMP
   (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, DEPTNO)
Values
   (7698, 'BLAKE', 'MANAGER', 7839, TO_DATE('05/01/1981 00:00:00', 'MM/DD/YYYY HH24:MI:SS'),
    2850, 30);
Insert into EMP
   (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, DEPTNO)
Values
   (7782, 'CLARK', 'MANAGER', 7839, TO_DATE('06/09/1981 00:00:00', 'MM/DD/YYYY HH24:MI:SS'),
    2450, 10);
Insert into EMP
   (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, DEPTNO)
Values
   (7788, 'SCOTT', 'ANALYST', 7566, TO_DATE('12/09/1982 00:00:00', 'MM/DD/YYYY HH24:MI:SS'),
    3000, 20);
Insert into EMP
   (EMPNO, ENAME, JOB, HIREDATE, SAL, DEPTNO)
Values
   (7839, 'KING', 'PRESIDENT', TO_DATE('11/17/1981 00:00:00', 'MM/DD/YYYY HH24:MI:SS'),
    5000, 10);
Insert into EMP
   (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO)
Values
   (7844, 'TURNER', 'SALESMAN', 7698, TO_DATE('09/08/1981 00:00:00', 'MM/DD/YYYY HH24:MI:SS'),
    1500, 0, 30);
Insert into EMP
   (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, DEPTNO)
Values
   (7876, 'ADAMS', 'CLERK', 7788, TO_DATE('01/12/1983 00:00:00', 'MM/DD/YYYY HH24:MI:SS'),
    1100, 20);
Insert into EMP
   (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, DEPTNO)
Values
   (7900, 'JAMES', 'CLERK', 7698, TO_DATE('12/03/1981 00:00:00', 'MM/DD/YYYY HH24:MI:SS'),
    950, 30);
Insert into EMP
   (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, DEPTNO)
Values
   (7902, 'FORD', 'ANALYST', 7566, TO_DATE('12/03/1981 00:00:00', 'MM/DD/YYYY HH24:MI:SS'),
    3000, 20);
Insert into EMP
   (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, DEPTNO)
Values
   (7934, 'MILLER', 'CLERK', 7782, TO_DATE('01/23/1982 00:00:00', 'MM/DD/YYYY HH24:MI:SS'),
    1300, 10);
COMMIT;