Oracle regexp_like word boundaries multiple words workaround - oracle

Question

As you know Oracle POSIX implementation of regexes does not support word boundaries. One workaround is suggested here:
Oracle REGEXP_LIKE and word boundaries
However it does not work if I want to, for instance select all 4 character strings. Consider this, for example:
myvar:=regexp_substr('test test','(^|\s|\W)[\S]{4}($|\s|\W)')
This obviously selects only the first occurrence. I do not know how to do this in the Oracle world, although normally it is simply (\b)[\S]{4}(\b). The problem is that most woraround rely on some nonexistent feature, like lookaround etc.

Answer 1

select xmlcast(xmlquery('for $token in ora:tokenize(concat(" ",$in)," ")
where string-length($token) = $size
return $token' passing 'test test' as "in", 4 as "size" returning content) as varchar2(2000)) word from dual;
Xquery and FLWOR expresion.
concat(" ",$in) - workaround if input string is null or it has only 1 matchting word.
ora:tokenize - tokenize string by "space"
string-length($token) = $size check if token has appropriate length.
xmlcast - convert xmltype to varchar2
Easy ? Any question:)

Answer 2

DECLARE
str VARCHAR2(200) := 'test test';
pattern VARCHAR2(200) := '(\w+)($|\s+|\W+)';
match VARCHAR2(200);
BEGIN
FOR i IN 1 .. REGEXP_COUNT( str, pattern ) LOOP
match := REGEXP_SUBSTR( str, pattern, 1, i, NULL, 1 );
IF LENGTH( match ) = 4 THEN
DBMS_OUTPUT.PUT_LINE( match );
END IF;
END LOOP;
END;
/
or (without using REGEXP_COUNT or the 6th parameter of REGEXP_SUBSTR that was introduced in 11G):
DECLARE
str VARCHAR2(200) := 'test test';
pattern CONSTANT VARCHAR2(3) := '\w+';
match VARCHAR2(200);
i NUMBER(4,0) := 1;
BEGIN
match := REGEXP_SUBSTR( str, pattern, 1, i );
WHILE match IS NOT NULL LOOP
IF LENGTH( match ) = 4 THEN
DBMS_OUTPUT.PUT_LINE( match );
END IF;
i := i + 1;
match := REGEXP_SUBSTR( str, pattern, 1, i );
END LOOP;
END;
/
Output:
test
test
If you want to use this in SQL then you can easily translate it into a pipelined function or a function that returns a collection.