Validate PO Box with RegExp_Like

Question

I'm trying to validate strings with variations of PO BOX, P.O. BOX 3232, Post Office Box 2323. The functions is like so:
CREATE or REPLACE FUNCTION FN_CHK_PO_BOX (v_str in VARCHAR2)
RETURN VARCHAR2
AS
BEGIN
   IF REGEXP_LIKE (v_str, '^[p|P][\s]*[o|O][\s]*[b|B][\s]*[o|O][\s]*[x|X][\s]*[a-zA-Z0-9]*|\b[P|p]+(OST|ost|o|O)?\.?\s*[O|o|0]+(ffice|FFICE)?\.?\s*[B|b][O|o|0]?[X|x]+\.?\s+[#]?(\d+)*(\D+)*\b$') THEN
          RETURN 'PO BOX Not Permitted';
   ELSE
          RETURN NULL;
   END IF;
END FN_CHK_PO_BOX;
select FN_CHK_PO_BOX('P.O. BOX 2323') from dual;For some reason it keeps evaluating to NULL and not returning "PO BOX Not Permitted" as expected. Not sure, any ideas?

Answer 1

The patterns depends on how flexible you want to be with the string, take a look at those rows that were left out:
SQL> with t as (
  2  select 1 num, 'P.O. BOX 2323' expr from dual union
  3  select 2, 'POST OFFICE BOX 2323' from dual union
  4  select 3, 'P O BOX 2323' from dual union
  5  select 4, 'P O BOX 2323' from dual union
  6  select 5, 'PO BOX 2323' from dual union
  7  select 6, 'p.o boX 2323' from dual union
  8  select 7, 'pO. BoX 2323' from dual union
  9  select 8, 'P. OFFICE BOX 2323' from dual union
10  select 9, 'POST O. BOX 2323' from dual union
11  select 10, 'POST OFF. BOX 2323' from dual union
12  select 11, 'P.O OFFICE BOX 2323' from dual union
13  select 12, 'POST OFFICE BOX 2323' from dual union
14  select 13, 'POST OFFICE BOX ' from dual union
15  select 13, 'POST OFFICE BOX ABC' from dual
16  )
17  select expr
18    from t
19  where regexp_like(expr
20        , '^((P\.?\s*O\.?)|(POST\s+OFFICE))\s*B\s*O\s*X\s*\d+$','i')
21  /
EXPR
P.O. BOX 2323
POST OFFICE BOX 2323
P O BOX 2323
P O BOX 2323
PO BOX 2323
p.o boX 2323
pO. BoX 2323
POST OFFICE BOX 2323
8 rows selected
SQL>