Get value between 2nd and 3rd comma

Question

I am trying to extract the state from an address where everything is in one column, heres an example:

2901 MAIN ST,CORNING,NY,14830

I have

Answer 1

select 
  regexp_substr('2901 MAIN ST,CORNING,NY,14830', '(.*?,){2}(.*?),', 1, 1, '', 2) 
from dual

In general,

n_th_component := 
  regexp_substr(string, '(.*?,){'||(n-1)||'}([^,]*)', 1, 1, '', 2);

Example:

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)

Answer 2

Regular expressions are a great way to do this sort of thing. SUBSTR and INSTR can also be used, however, by taking advantage of the 4th parameter of INSTR, nth_appearance:

select INSTR(mystring,',',1,1) AS first_comma
      ,INSTR(mystring,',',1,2) AS second_comma
      ,SUBSTR(mystring
             ,INSTR(mystring,',',1,1) + 1
             ,INSTR(mystring,',',1,2)
              - INSTR(mystring,',',1,1)
              - 1)
       AS middle_bit
FROM
(select 'hello,world,NY,11725-1234' as mystring from dual);

FIRST_COMMA  SECOND_COMMA  MIDDLE_BIT
===========  ============  ==========
          6            12  world