query to extract grade change on employee assignment form

Hi Experts ,

I have requirement to extract data from system where grade change are required w.e.f 01-Jan-2018

created following query to

select

papf.EMPLOYEE_NUMBER

,papf.full_name

,to_char(paaf.LAST_UPDATE_DATE, 'DD-MON-YYYY')   Date_change

,pgrade.NAME

from

apps.per_all_people_f       PAPF

,apps.per_all_assignments_F  PAAF

,apps.per_grades_vl           pgrade

where

papf.person_id = paaf.person_id

and 

paaf.GRADE_ID = pgrade.GRADE_ID

and papf.CURRENT_EMPLOYEE_FLAG = 'Y'

and papf.PERSON_TYPE_ID  <> '1130'

and paaf.LAST_UPDATE_DATE > '01-JAN-2018'

but query is extracting all record update on