The missing \b regular expression special character in Oracle.

Oracle's regular expressions don't support the special regular expression character \b, at least not in Oracle 11i.

Consider the following table:

create table tq84_word_boundaries ( txt varchar2(50) ); insert into tq84_word_boundaries values ('AFooABarAndABaz' ); insert into tq84_word_boundaries values ('A FooA BarAndABaz' ); insert into tq84_word_boundaries values ('A Foo, a Bar and a Baz'); insert into tq84_word_boundaries values ('A Foo without a Baz' ); insert into tq84_word_boundaries values ('Foo Bar, Baz' ); insert into tq84_word_boundaries values ('Is it a Foo?' ); insert into tq84_word_boundaries values ('Bar-Foo-Baz' );

Now, I want to find all records that contain the exact word Foo. That is, I want, for example A Foo without a Baz (the fourth record), but I don't want A FooA BarAndABaz (the second record) because FooA is not the exact word Foo

If Oracle supported \b I could use

select * from tq84_word_boundaries where regexp_like(txt, '\bFoo\b');

Yet, Oracle, does not support it and no record is returned.

To improve matters, I could try

select * from tq84_word_boundaries where regexp_like(txt, '\sFoo\s');

This approach returns

TXT -------------------------------------------------- A Foo without a Baz

A bit better, but far from perfect. For example, the fifth record (Foo Bar, Baz) is not returned, because the \s doesn't match start of line. So, I improve the where condition:

select * from tq84_word_boundaries where regexp_like(txt, '(^|\s)Foo($|\s)');

The record is now returned:

TXT -------------------------------------------------- A Foo without a Baz Foo Bar, Baz

Yet again, this is far from perfect. I need also record records where Foo is followed or lead by a non word character (such as ? or -):

select * from tq84_word_boundaries where regexp_like(txt, '(^|\s|\W)Foo($|\s|\W)');

This returns

TXT -------------------------------------------------- A Foo, a Bar and a Baz A Foo without a Baz Foo Bar, Baz Is it a Foo? Bar-Foo-Baz

I think I can live with it.

Links

Source code on github