select
regexp_substr('2901 MAIN ST,CORNING,NY,14830', '(.*?,){2}(.*?),', 1, 1, '', 2)
from dual
En général,
n_th_component :=
regexp_substr(string, '(.*?,){'||(n-1)||'}([^,]*)', 1, 1, '', 2);
Exemple :
select
n,
regexp_substr('2901 MAIN ST,CORNING,NY,14830',
'(.*?,){'||(n-1)||'}([^,]*)', 1, 1, '', 2)
from (select level n from dual connect by level <= 4)