with ev as
(
-- Тестовые данные
SELECT 'GRANT'  access_act, to_date('10.10.2008','DD.MM.YYYY') as dt, 'u1' as usr from dual union all
SELECT 'REVOKE' access_act, to_date('14.10.2008','DD.MM.YYYY') as dt, 'u1' as usr from dual union all
SELECT 'GRANT'  access_act, to_date('22.10.2008','DD.MM.YYYY') as dt, 'u1' as usr from dual union all
SELECT 'GRANT'  access_act, to_date('11.11.2008','DD.MM.YYYY') as dt, 'u2' as usr from dual union all
SELECT 'GRANT'  access_act, to_date('09.10.2008','DD.MM.YYYY') as dt, 'u3' as usr from dual union all
SELECT 'REVOKE' access_act, to_date('20.10.2008','DD.MM.YYYY') as dt, 'u3' as usr from dual union all
SELECT 'GRANT'  access_act, to_date('12.12.2008','DD.MM.YYYY') as dt, 'u3' as usr from dual
)

-- кто имел доступ на указанную дату
SELECT usr
FROM ev
WHERE ev.access_act = 'GRANT'
  and (ev.usr,ev.dt) in
  (SELECT ev1.usr, max(ev1.dt) FROM ev ev1
   WHERE ev1.dt <= to_date('01.11.2008','DD.MM.YYYY') GROUP BY ev1.usr)
union
-- Кто новый получил доступ в интервале
SELECT usr
FROM ev 
WHERE ev.access_act = 'GRANT'
  and ev.dt between to_date('01.11.2008','DD.MM.YYYY') and to_date('01.12.2008','DD.MM.YYYY')