with t1 as
 (select level lev from dual connect by rownum <= 10),
t2 as
 (select 2 nach, 3 kon from dual union select 6 nach, 8 kon from dual)
---------------------------------------------------------------- 
select t1.lev, DECODE(tt.lev,NULL,'N','Y')
  from t1,
       (select t1.lev from t1, t2 where t1.lev between t2.nach and t2.kon) tt
 where t1.lev = tt.lev(+)
order by t1.lev

with t1 as
 (select level lev from dual connect by rownum <= 10),
t2 as
 (select 2 nach, 3 kon from dual union select 6 nach, 8 kon from dual)
---------------------------------------------------------------- 
select lev, flag
  from (select row_number() over(partition by lev order by flag desc) rn,
               lev,
               flag
          from (select distinct lev, flag
                  from (select t1.lev,
                               case
                                 when t1.lev between t2.nach and t2.kon then
                                  'Y'
                                 else
                                  'N'
                               end flag
                          from t1, t2)))
 where rn = 1
 order by lev