Help with Regular Expressions and regexp_replace

Question

Oh great Oracle Guru can I can gets some help
I need to clean up the phone numbers that have been entered in Oracle eBusiness per_phones table. Some of the phone numbers have dashes, some have spaces and some have char. I would just like to take all the digits out and then re-format the number.
Ex.
914-123-1234 .. output [phone]
9141231234 ..again [phone]
914 123 1234 .. [phone]
myphone ... just null
(914)-123-1234.. [phone]
I really tried to understand the regular expressions statments, but for some reason I just can't understand it.

Answer 1

Hi,
Welcome to the forum!
I would create a user-defined function for this. I expect there will be a lot of exceptions to the regular rules (for example, strings that do not contain exactly 10 digits, such as '1-800-987-6543') that can be handled, but would require lots of nested fucntions and othwer complicted code if you had to do it in a single statement.
If you really want to do it with a regular expression:
SELECT     phone_txt
,     REGEXP_REPLACE ( phone_txt
                 , '^\D*'          || -- 0 or more non-digits at the beginning of the string
                       '(\d\d\d)'     || -- \1 = 3 consecutive digits
                '\D*'          || -- 0 or more non-digits
                       '(\d\d\d)'     || -- \2 = 3 consecutive digits
                '\D*'          || -- 0 or more non-digits
                       '(\d\d\d)'     || -- \3 = 4 consecutive digits
                '\D*$'             -- 0 or more non-digits at the end of the string
                 , '(\1) \2-\3'
                 )          AS new_phone_txt
FROM    table_x
;