Query to get List of Employees Current and Previous Assignment Details in Oracle APPS

SELECT ppf.employee_number,

         paaf.assignment_number,

         ppf.full_name,

         paaf.organization_id current_org_id,

         paaf.effective_start_date current_org_start_date,

         (SELECT name

            FROM hr_all_organization_units

           WHERE organization_id = paaf.organization_id)

            current_org_name,

         paaf_previous.effective_start_date previous_org_start_date,

         paaf_previous.organization_id previous_org_id,

         (SELECT name

            FROM hr_all_organization_units

           WHERE organization_id = paaf_previous.organization_id)

            previous_org_name

    FROM per_all_assignments_f paaf,

         per_all_assignments_f paaf_previous,

         pay_people_groups ppg,

         pay_people_groups ppg_previous,

         per_all_people_f ppf

   WHERE paaf_previous.effective_end_date + 1 = paaf.effective_start_date

     AND paaf_previous.assignment_id = paaf.assignment_id

     AND paaf_previous.assignment_type = 'E'

     AND paaf.assignment_type = 'E'

     AND paaf.organization_id <> paaf_previous.organization_id

     AND paaf.PEOPLE_GROUP_ID = ppg.people_group_id

     AND paaf_previous.PEOPLE_GROUP_ID = ppg_previous.people_group_id

     AND paaf.effective_start_date BETWEEN ppf.effective_start_date

                                       AND ppf.effective_end_date

     AND paaf.person_id = ppf.person_id

AND ppf.employee_number = '1234567890'

ORDER BY paaf_previous.effective_start_date DESC