Question

I am having a problem with matching word boundaries with REGEXP_LIKE. The following query returns a single row, as expected.

select 1 from dual
where regexp_like('DOES TEST WORK HERE','TEST');

But I want to match on word boundaries as well. So, adding the “\b” characters gives this query

select 1 from dual
where regexp_like('DOES TEST WORK HERE','\bTEST\b');

Running this returns zero rows. Any ideas?

Answer 1

I believe you want to try

 select 1 from dual 
  where regexp_like ('does test work here', '(^|\s)test(\s|$)');

because the \b does not appear on this list: Perl-influenced Extensions in Oracle Regular Expressions

The \s makes sure that test starts and ends in a whitespace. This is not sufficient, however, since the string test could also appear at the very start or end of the string being matched. Therefore, I use the alternative (indicated by the |) ^ for start of string and $ for end of string.

Update (after 3 years+)…
As it happens, I needed this functionality today, and it appears to me, that even better a regular expression is (^|\s|\W)test($|\s|\W) (The missing \b regular expression special character in Oracle).