ACTUALIZAR Nueva respuesta basada en los comentarios de OP.
Podrías usar ANALYTIC función ROW_NUMBER y LAG .Algo así como, método de inicio de grupo:
SQL> WITH DATA AS(
2 SELECT 100 EmployeeID, 'IT' Department, to_date('01.07.2014','DD.MM.YYYY') dt FROM dual UNION ALL
3 SELECT 100, 'IT', to_date('01.08.2014','DD.MM.YYYY') dt from dual union all
4 select 100, 'IT', to_date('01.09.2014','DD.MM.YYYY') dt from dual union all
5 SELECT 100, 'HR', to_date('01.10.2014','DD.MM.YYYY') dt from dual union all
6 select 100, 'HR', to_date('01.11.2014','DD.MM.YYYY') dt from dual union all
7 SELECT 100, 'CC', to_date('01.12.2014','DD.MM.YYYY') dt from dual union all
8 select 100, 'IT', to_date('01.01.2015','DD.MM.YYYY') dt from dual union all
9 select 100, 'IT', to_date('01.02.2015','DD.MM.YYYY') dt from dual
10 )
11 SELECT EmployeeID,
12 Department,
13 DT
14 FROM
15 (SELECT *
16 FROM
17 (SELECT t.*,
18 CASE
19 WHEN Department = lag(Department) over (PARTITION BY EmployeeID ORDER BY dt)
20 THEN 0
21 ELSE 1
22 END gap
23 FROM DATA t
24 ) T
25 WHERE GAP = 1
26 ORDER BY DT DESC
27 )
28 WHERE ROWNUM = 1
29 /
EMPLOYEEID DE DT
---------- -- ---------
100 IT 01-JAN-15
SQL>
RESPUESTA ANTIGUA
Por ejemplo,
SQL> WITH DATA AS(
2 SELECT 100 EmployeeID, 'IT' Department, to_date('01.07.2014','DD.MM.YYYY') dt FROM dual UNION ALL
3 SELECT 100, 'IT', to_date('01.08.2014','DD.MM.YYYY') dt from dual union all
4 select 100, 'IT', to_date('01.09.2014','DD.MM.YYYY') dt from dual union all
5 SELECT 100, 'HR', to_date('01.10.2014','DD.MM.YYYY') dt from dual union all
6 select 100, 'HR', to_date('01.11.2014','DD.MM.YYYY') dt from dual union all
7 SELECT 100, 'CC', to_date('01.12.2014','DD.MM.YYYY') dt from dual union all
8 select 100, 'IT', to_date('01.01.2015','DD.MM.YYYY') dt from dual union all
9 select 100, 'IT', to_date('01.02.2015','DD.MM.YYYY') dt from dual
10 )
11 SELECT*
12 FROM
13 (SELECT t.*,
14 row_number() OVER(PARTITION BY department ORDER BY dt DESC) rn
15 FROM DATA t
16 )
17 WHERE rn = 1
18 /
EMPLOYEEID DE DT RN
---------- -- --------- ----------
100 CC 01-DEC-14 1
100 HR 01-NOV-14 1
100 IT 01-FEB-15 1
SQL>
