Query to Get Leave Details on Specified dates

SELECT CASE

          WHEN :p_date_start > paa.date_start THEN :p_date_start

          WHEN :p_date_start < paa.date_start THEN paa.date_start

          WHEN :p_date_start = paa.date_start THEN :p_date_start

       END

          start_date,

       CASE

          WHEN :p_date_end > paa.date_end THEN paa.date_end

          WHEN :p_date_end < paa.date_end THEN :p_date_end

          WHEN :p_date_end = paa.date_end THEN :p_date_end

       END

          end_date

  FROM per_absence_attendances paa,

       per_absence_attendance_types paat,

       per_all_assignments_f paaf

 WHERE paat.absence_attendance_type_id = paa.absence_attendance_type_id

       AND UPPER (paat.name) = UPPER (:p_leave_type)

       AND (   paa.date_start BETWEEN :p_date_start AND :p_date_end

            OR paa.date_end BETWEEN :p_date_start AND :p_date_end

            OR :p_date_start BETWEEN paa.date_start AND paa.date_end

            OR :p_date_end BETWEEN paa.date_start AND paa.date_end)

       AND paaf.person_id = paa.person_id

       AND paaf.primary_flag = 'Y'

       AND paaf.assignment_type = 'E'

       AND paaf.assignment_status_type_id IN (1, 2)

       AND :p_date_end BETWEEN paaf.effective_start_date

                           AND paaf.effective_end_date

       AND paaf.assignment_id = :p_assignment_id