Use a Regex in SQL statement to extract several strings - Oracle - sql

Question

I want to extract some strings from the VAL column, according the regex furhter below in bold. This is an example of the data I have in source :
Table1
-----------------
ID VAL
-----------------
1 GR-RDE
2 GR-RZA-RDE
3 GR-RZA-RDE_RZA
4 GR-RGS
5 GR-RZA-OR-ORC
6 GR-RZA-RDE-OR-ORC_RZA
Desired result :
> Output
-----------------
ID RESULT
-----------------
1 RDE
2 RZA
2 RDE
3 RZA
3 RDE
4 RGS
5 RZA
5 OR
6 RZA
6 RDE
6 OR
To do that, I've done this regex :
(?<=-)(RDE|RZA|RGS|OR)(?![A-Z])
(?<=-) : checks that the character before is '-'
(RDE|RZA|RGS|OR) : search for 'RDE', 'RZA', 'RGS', 'OR' strings
(?![A-Z]) : ignore the string if it's followed by a letter
The regex works perfectly and it ignores all the unwhanted parts :
My problem is that I don't find the way to use this regex in a SQL statement (Oracle database). I've tried to perform a test with something like this, which returns Null :
select REGEXP_SUBSTR(VAL,'(?<=-)(RDE|RZA|RGS|OR)(?![A-Z])') from Table1;

Answer 1

SQL Fiddle
Oracle 11g R2 Schema Setup:
CREATE TABLE Table1 ( ID, VAL ) AS
SELECT 1, 'GR-RDE' FROM DUAL UNION ALL
SELECT 2, 'GR-RZA-RDE' FROM DUAL UNION ALL
SELECT 3, 'GR-RZA-RDE_RZA' FROM DUAL UNION ALL
SELECT 4, 'GR-RGS' FROM DUAL UNION ALL
SELECT 5, 'GR-RZA-OR-ORC' FROM DUAL UNION ALL
SELECT 6, 'GR-RZA-RDE-OR-ORC_RZA' FROM DUAL
Query 1:
WITH words ( id, val, lvl, str, maxlvl ) AS (
SELECT id,
val,
1,
REGEXP_SUBSTR( val, '[A-Z]+', 1, 1 ),
REGEXP_COUNT( val, '[A-Z]+' )
FROM table1
UNION ALL
SELECT id,
val,
lvl + 1,
REGEXP_SUBSTR( val, '[A-Z]+', 1, lvl + 1 ),
maxlvl
FROM words
WHERE lvl < maxlvl
)
SELECT id, str, lvl
FROM words
ORDER BY id, lvl
Results:
| ID | STR | LVL |
|----|-----|-----|
| 1 | GR | 1 |
| 1 | RDE | 2 |
| 2 | GR | 1 |
| 2 | RZA | 2 |
| 2 | RDE | 3 |
| 3 | GR | 1 |
| 3 | RZA | 2 |
| 3 | RDE | 3 |
| 3 | RZA | 4 |
| 4 | GR | 1 |
| 4 | RGS | 2 |
| 5 | GR | 1 |
| 5 | RZA | 2 |
| 5 | OR | 3 |
| 5 | ORC | 4 |
| 6 | GR | 1 |
| 6 | RZA | 2 |
| 6 | RDE | 3 |
| 6 | OR | 4 |
| 6 | ORC | 5 |
| 6 | RZA | 6 |
Query 2:
SELECT t.id, w.COLUMN_VALUE AS str
FROM Table1 t
CROSS JOIN
TABLE(
CAST(
MULTISET(
SELECT REGEXP_SUBSTR( t.val, '[A-Z]+', 1, LEVEL )
FROM DUAL
CONNECT BY LEVEL <= REGEXP_COUNT( t.val, '[A-Z]+' )
) AS SYS.ODCIVARCHAR2LIST
)
) w
Results:
| ID | STR |
|----|-----|
| 1 | GR |
| 1 | RDE |
| 2 | GR |
| 2 | RZA |
| 2 | RDE |
| 3 | GR |
| 3 | RZA |
| 3 | RDE |
| 3 | RZA |
| 4 | GR |
| 4 | RGS |
| 5 | GR |
| 5 | RZA |
| 5 | OR |
| 5 | ORC |
| 6 | GR |
| 6 | RZA |
| 6 | RDE |
| 6 | OR |
| 6 | ORC |
| 6 | RZA |