Regexp_like vs regex validators online - diferent results - regex

Question

I have a regex expression for email validation using plsql that is giving me some headaches... :)
This is the condition I'm using for an email (rercear12345#gmail.com) validation:
IF NOT REGEXP_LIKE (user_email, '^([\w\-\.]+)#((\[([0-9]{1,3}\.){3}[0-9]{1,3}\])|(([\w\-]+\.)+)([a-zA-Z]{2,4}))$') THEN
control := FALSE;
dbms_output.put_line('EMAIL '||C.user_email||' not according to regex');
END IF;
If I make a select based on the expression I don't get any values either:
Select * from TABLE_X where REGEXP_LIKE (user_email, '^([\w\-\.]+)#((\[([0-9]{1,3}\.){3}[0-9]{1,3}\])|(([\w\-]+\.)+)([a-zA-Z]{2,4}))$');
Using regex101.com I get full match with this email: rercear12345#gmail.com
Any idea?

Answer 1

The regular expression syntax that Oracle supports is in the documentation.
It seems Oracle doesn't understand the \w inside the []. You can expand that to:
with table_x (user_email) as (
select 'rercear12345#gmail.com' from dual
union all
select 'bad name#gmail.com' from dual
)
Select * from TABLE_X
where REGEXP_LIKE (user_email, '^[a-zA-Z_0-9.-]+#((\[([0-9]{1,3}\.){3}[0-9]{1,3}\])|([a-zA-Z_0-9-]+.)+[a-zA-Z]{2,4})$');
USER_EMAIL
----------------------
rercear12345#gmail.com
You don't need to escape the . or - inside the square brackets, by doing that you would allow literal backslashes to be matched.
This sort of requirement has come up before - e.g. here - but you seem be allowing IP address octets instead of FQDNs, enclosed in literal square brackets, which is unusual.
As #BobJarvis said you could also use the [:alnum:] but would still need to include underscore. That could allow non-ASCII 'letter' characters you aren't expecting; though they may be valid, as are other symbols you exclude; you seem to be following the 'common advice' mentioned in that article though.