Supervisor Change.Pls help

Question

I have a employee table
person_id employee_number full_name supervisor_name start_date end_date
1           100               Cob     Don             01-JAN-2000   31-DEC-2000
1           100               Cobb    Don             01-JAN-2001   30-JUN-2001
1           100               Cobb     Smith           01-JUL-2001   31-DEC-2001person_id start_date and end_date is composite primary key
I need a output where employee's supervisor changed between two dates
employee_number full_name old_supervisor_name  new_supervisor_name
100               cobb          Don                  SmithPlease let me know if i am not clear

Answer 1

Try this:
WITH employee AS
(SELECT 1 person_id, 100 employee_number, 'Cobb' full_name, 'Don' supervisor_name, TO_DATE('01-JAN-2000') start_date, TO_DATE('31-DEC-2000') end_date FROM dual UNION ALL
SELECT 1 person_id, 100 employee_number, 'Cobb' full_name, 'Don' supervisor_name, TO_DATE('01-JAN-2001') start_date, TO_DATE('30-JUN-2001') end_date FROM dual UNION ALL
SELECT 1 person_id, 100 employee_number, 'Cobb' full_name, 'Smith' supervisor_name, TO_DATE('01-JUL-2001') start_date, TO_DATE('31-DEC-2001') end_date FROM dual UNION ALL
SELECT 2 person_id, 110 employee_number, 'Jones' full_name, 'Mark' supervisor_name, TO_DATE('01-JAN-2000') start_date, TO_DATE('31-DEC-2001') end_date FROM dual)
SELECT employee_number,
       full_name,
       supervisor_name,
       new_supervisor_name
FROM  (SELECT employee_number,
              full_name,
              supervisor_name,
              LEAD(supervisor_name) OVER (PARTITION BY employee_number ORDER BY employee_number, start_date) new_supervisor_name
       FROM   employee)
WHERE  supervisor_name != NVL(new_supervisor_name, supervisor_name)