--1
with
t3 as(select 3 id, 'fizz' text from dual),
t5 as(select 5 id, 'buzz' text from dual),
rs as(select rownum r from dual connect by rownum < 101)
select listagg(nvl(t3.text||t5.text, r), ',') within group (order by r)
  from rs, t3, t5
 where t3.id(+) = 3 - mod(rs.r, 3)
   and t5.id(+) = 5 - mod(rs.r, 5)

union all

--2
select listagg(case
   when mod(rownum, 15)=0 then 'fizzbuzz'
   when mod(rownum, 5)=0 then 'buzz'
   when mod(rownum, 3)=0 then 'fizz'
   else ''||rownum end, ',') within group(order by rownum)
  from dual connect by rownum < 101