Oracle: Replacing non-numeric chars in a string

Question

I have a field in my database where users have saved free-form telephone numbers. As a result, the data has all sorts of different formatting:

• (area) nnn-nnnn
• area-nnn-nnnn
• area.nnn.nnnn
• etc

I would like to strip out all the non-numeric characters and just store the digits, but I can't find a simple way to do this. Is it possible without using one REPLACE for each char?

Answer 1

You can use REGEXP_REPLACE since Oracle 10:

SELECT REGEXP_REPLACE('+34 (947) 123 456 ext. 2013', '[^0-9]+', '') FROM DUAL 

This example returns 349471234562013.

Alternative syntaxes include:

• POSIX character classes:

  '[^[:digit:]]+' 

• Perl-influenced extensions (since Oracle 11):

  '\D+' 

Answer 2

For older versions of Oracle that don't support regular expressions:

select translate (phone_no,'0'||translate (phone_no,'x0123456789','x'),'0') from mytable; 

The inner translate gets all the non-digit characters from the phone number, and the outer translate then removes them from the phone number.