Grade Change Query in Oracle HRMS

select papf.employee_number,papf.full_name,

pg_old.name old_grade, pg_new.name new_grade,paaf_new.effective_start_date change_date

from apps.per_all_people_f papf,

apps.per_all_assignments_f paaf_old,

apps.per_grades pg_old,

apps.per_all_assignments_f paaf_new,

apps.per_grades pg_new

where 1=1

and papf.person_id = paaf_old.person_id

and papf.person_id = paaf_new.person_id

and paaf_old.person_id = paaf_new.person_id

and paaf_old.assignment_type = 'E'

and paaf_old.primary_flag = 'Y'

and paaf_new.assignment_type = 'E'

and paaf_new.primary_flag = 'Y'

and pg_old.grade_id = paaf_old.grade_id

and pg_new.grade_id = paaf_new.grade_id

and paaf_old.grade_id <> paaf_new.grade_id

and trunc(paaf_old.effective_end_date)+1 =trunc(paaf_new.effective_start_date)

and trunc(sysdate) between papf.effective_start_date and papf.effective_end_date

and  trunc(sysdate) between paaf_new.effective_start_date and paaf_new.effective_end_date