Is there any document available for understanding the regular expressions used by regular expression functions like REGEXP_SUBSTR, REGEXP_SIMILAR etc.
There's no Teradata-specific documentation on regex, but there are many books and online resources available, simply google for "regular expression".
Caution, there are different dialects for regex, but Teradata usually follows the Perl variant (Perl Compatible Regular Expressions = PCRE).
Thanks Dieter. That is why I was wondering why some of the regular expressions are not working. I was using regular expressions used in sed, awk.