In today's tip, we will look at a few practical examples of regular expressions in Oracle.

Example 1: Credit card numbers usually have the format: 1234-1234-1234-1234
We look for two blocks of 4 in a string with numbers and a minus in between and replace each block with: xxxx-xxxx:

• [[:digit:]] stands for numbers only
• [4} 4 Numbers

select regexp_replace(
'1234-5678-1111-2222',
'[[:digit:]]{4}-[[:digit:]]{4}','xxxx-xxxx') from dual;

Result: xxxx-xxxx-xxxx-xxxx

Or we look for four blocks of 4 with numbers and replace this with: XXXX:

select regexp_replace(
'1234-5678-1111-2222',
'[[:digit:]]{4}','xxxx') 
from dual;

Result: xxxx-xxxx-xxxx-xxxx

Only the last block of 4 is to be issued:

select regexp_replace(
'1234-5678-1111-2222',
'([[:digit:]]{4})(-)([[:digit:]]{4})(-)([[:digit:]]{4})(-)([[:digit:]]{4})','XXXX-XXXX-XXXX-\7') from dual;

Result:

XXXX-XXXX-XXXX-2222

Alternatively, instead of [[:digit:]] with \d replace

select regexp_replace(
'1234-5678-1111-2222',
'\d{4}','x') 
from dual;

Result: x-x-x-x

Beispiel 2: Wir löschen einige HTML Tags in einem String:

• \/?div finds div, 
• \/?p finds p and 
• \/?strong findsstrong Tags 
• (/ is a special Character and have to be \ escaped)

select regexp_replace(
'<div>Hallo</div><strong> Kurs</strong>',
'(<\/?div>|<\/?p>|<\/?strong>)','') 
from dual;

or we delete all HTML tags in the string

select regexp_replace(
'<div>Hallo</div><strong> Training</strong>',
'<\/?[^>]*>,'') 
from dual;

This was a small selection of examples, which we are constantly expanding. Or you can come to the PL/SQL or PL/SQL II course, for example, where these topics are also discussed in detail.