with test as
(
     select 'aaa' a,'1,2,3' c from dual union all
     select 'bbb' a,'1,2' c from dual
)
    
select a,substr(t.ca,instr(t.ca, ',', 1, c.lv) + 1,instr(t.ca, ',', 1, c.lv + 1) -(instr(t.ca, ',', 1, c.lv) + 1)) AS c
from (select a,',' || c || ',' AS ca,length(c || ',') - nvl(length(REPLACE(c, ',')), 0) AS cnt FROM test)t,
    (select LEVEL lv from dual CONNECT BY LEVEL <= 100) c where c.lv <= t.cnt
order by a

    a    c
---------------------
1    aaa    1
2    aaa    2
3    aaa    3
4    bbb    2
5    bbb    1

------解决方案--------------------
SQL code
with t as(
select 'a,b,c,d' str from dual
)
SELECT regexp_substr(str, '[^,]+', 1, level)
  from t
connect by level <= length(str) - length(replace(str, ',', '')) + 1;
REGEXP_SUBSTR(STR,'[^,]+',1,LE
------------------------------
a
b
c
d

------解决方案--------------------
select regexp_substr(values, '[^,]+',1,levle)
from t
connect by level <= length(values) - length(replace(values,',','')) + 1