SQL help. Identify changes on a field.

Question

Greetings!
PS/SQL is not an option for me. I need help to use SQL, if possible for the following scenario.
Oracle 10G.
Table : JOB_DATA
EMPLID, DATE_EFF, DEPTID, JOBCODE
100, 11/1/2012, 34567, MNG
100, 10/1/2012, 34567, SUP
100, 9/1/2012, 28967, MNG
100, 8/15/2012, 28967, SUP
100,6/30/2012,15879, MNG
I need to get the following records only, that is ,whenever changes in Department ID.
100, 10/1/2012, 34567, SUP
100, 8/15/2012, 28967, SUP
100,6/30/2012,15879, MNG
Thanks in advance.

Answer 1

Hi Rama,
Next time please post table structure and sample data.
Please read SQL and PL/SQL FAQ
Here another way to do it:
WITH job_data AS
   SELECT 100 emplid, TO_DATE('11/1/2012', 'MM/DD/YYYY') date_eff, 34567 deptid, 'MNG' jobcode FROM DUAL UNION ALL
   SELECT 100 emplid, TO_DATE('10/1/2012', 'MM/DD/YYYY') date_eff, 34567 deptid, 'SUP' jobcode FROM DUAL UNION ALL
   SELECT 100 emplid, TO_DATE('9/1/2012' , 'MM/DD/YYYY') date_eff, 28967 deptid, 'MNG' jobcode FROM DUAL UNION ALL
   SELECT 100 emplid, TO_DATE('8/15/2012', 'MM/DD/YYYY') date_eff, 28967 deptid, 'SUP' jobcode FROM DUAL UNION ALL
   SELECT 100 emplid, TO_DATE('6/30/2012', 'MM/DD/YYYY') date_eff, 15879 deptid, 'MNG' jobcode FROM DUAL
SELECT emplid, date_eff, deptid, jobcode
  FROM (SELECT j.*
             , DENSE_RANK() OVER (PARTITION BY emplid, deptid ORDER BY date_eff) rn
         FROM job_data j
WHERE rn = 1
ORDER BY date_eff DESC;
    EMPLID DATE_EFF       DEPTID JOBCODE
       100 10/01/2012      34567 SUP   
       100 08/15/2012      28967 SUP   
       100 06/30/2012      15879 MNG   PARTITION BY emplid, deptid means that any time this combination of value is changing the rank will start again from 1.
The rank is ordered by date_eff.
I assume that you don't have the same date_eff for more than one record. If you have same date_eff for more than one record you need to explain what will be the logic in this case.
Regards.
Al
Edited by: Alberto Faenza on Nov 15, 2012 8:50 PM
Clarifications added