How do I extract a pattern from a table in Oracle 11g? - regex

Question

I want to extract text from a column using regular expressions in Oracle 11g. I have 2 queries that do the job but I'm looking for a (cleaner/nicer) way to do it. Maybe combining the queries into one or a new equivalent query. Here they are:
Query 1: identify rows that match a pattern:
select column1 from table1 where regexp_like(column1, pattern);
Query 2: extract all matched text from a matching row.
select regexp_substr(matching_row, pattern, 1, level)
from dual
connect by level < regexp_count(matching_row, pattern);
I use PL/SQL to glue these 2 queries together, but it's messy and clumsy. How can I combine them into 1 query. Thank you.
UPDATE: sample data for pattern 'BC':
row 1: ABCD
row 2: BCFBC
row 3: HIJ
row 4: GBC
Expected result is a table of 4 rows of 'BC'.

Answer 1

You can also do it in one query, functions/procedures/packages not required:
WITH t1 AS (
SELECT 'ABCD' c1 FROM dual
UNION
SELECT 'BCFBC' FROM dual
UNION
SELECT 'HIJ' FROM dual
UNION
SELECT 'GBC' FROM dual
)
SELECT c1, regexp_substr(c1, 'BC', 1, d.l, 'i') thePattern, d.l occurrence
FROM t1 CROSS JOIN (SELECT LEVEL l FROM dual CONNECT BY LEVEL < 200) d
WHERE regexp_like(c1,'BC','i')
AND d.l <= regexp_count(c1,'BC');
C1 THEPATTERN OCCURRENCE
----- -------------------- ----------
ABCD BC 1
BCFBC BC 1
BCFBC BC 2
GBC BC 1
SQL>
I've arbitrarily limited the number of occurrences to search for at 200, YMMV.

Answer 2

Actually there is an elegant way to do this in one query, if you do not mind to run some extra miles. Please note that this is just a sketch, I have not run it, you'll probably have to correct a few typos in it.
create or replace package yo_package is
type word_t is record (word varchar2(4000));
type words_t is table of word_t;
end;
/
create or replace package body yo_package is
function table_function(in_cur in sys_refcursor, pattern in varchar2)
return words_t
pipelined parallel_enable (partition in_cur by any)
is
next varchar2(4000);
match varchar2(4000);
word_rec word_t;
begin
word_rec.word = null;
loop
fetch in_cur into next;
exit when in_cur%notfound;
--this you inner loop where you loop through the matches within next
--you have to implement this
loop
--TODO get the next match from next
word_rec.word := match;
pipe row (word_rec);
end loop;
end loop;
end table_function;
end;
/
select *
from table(
yo_package.table_function(
cursor(
--this is your first select
select column1 from table1 where regexp_like(column1, pattern)
)
)