Repeating rows in sql

Question

Hello All,
This is the situation I am stuck with.
I am having a table which is recording the history of movement of a employee
emp_movement(EMP_ID,
START_DATE,
BACK_DATE,
MOVED_FROM (foreign key from dept),
MOVED_TO(foreign key from dept))
I want a report showing the result like this:
Start Date, Moved from Dept Name, Moved to Dept Name, End Date
I am having a query like this:
WITH PT AS(select EMP_ID, DEPT_NAME DNAME
from     EMP_MOVEMENT,
DEPT
where EMP_ID = :P105_EMP_ID
and DEPT.DEPT_ID = MOVED_TO)
select distinct "START_DATE",
"BACK_DATE",
DEPT_NAME,
     DNAME
from     EMP_MOVEMENT EM,
DEPT, PT
where EM.EMP_ID = PT.EMP_ID
and DEPT.DEPT_ID = MOVED_FROM
order by 1
but when there are two movements for a employee, this query is showing 4 rows in result.
Please help me with this.
Thanks
Tauceef

Answer 1

Hi, Tauceef,
You can do it with a self-join, like you tried, but I think it's easier using the analytic LAG function:
SELECT    em.emp_id
,       em.start_date
,       em.back_date
,       dept.dept_name                                        AS dname
,       LAG (em.start_date)   OVER (PARTITION BY em.emp_id ORDER BY em.start_date)     AS prev_start_date
,       LAG (em.back_date)    OVER (PARTITION BY em.emp_id ORDER BY em.start_date)     AS prev_start_date
,       LAG (dept.dept_name)  OVER (PARTITION BY em.emp_id ORDER BY em.start_date)     AS prev_dname
FROM       emp_movement     em
,       dept
WHERE       dept.dept_id     = em.moved_from
-- AND       em.emp_id     = :p105_emp_id          -- If desired
ORDER BY  em.emp_id
,            em.start_date
I hope this answers your question.
If not, post a little sample data (CREATE TABLE and INSERT statements, relevant columns only) for all tables, and also post the results you want from that data.
Explain, using specific examples, how you get those results from that data.
Always say which version of Oracle you're using.