Oracle 23c

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ALTER SESSION SET NLS_DATE_FORMAT = 'YYYY-MM-DD HH24:MI:SS';
CREATE TABLE table_name (value) AS
SELECT 'Data 1__##__Data Two__##__Third Data__##__4th Data__##__' FROM DUAL;
1 rows affected

WITH bounds (value, spos, epos) AS (
  SELECT value,
         1,
         INSTR(value, '__##__', 1)
  FROM   table_name
UNION ALL
  SELECT value,
         epos + 6,
         INSTR(value, '__##__', epos + 6)
  FROM   bounds
  WHERE  epos > 0
) SEARCH DEPTH FIRST BY value SET order_id
SELECT SUBSTR(value, spos, epos - spos) AS value 
FROM   bounds
WHERE  epos > 0


VALUE


Data 1

Data Two

Third Data

4th Data


SELECT REGEXP_SUBSTR(
         'Data 1__##__Data Two__##__Third Data__##__4th Data__##__', 
         '(.*?)__##__',
         1,
         LEVEL,
         NULL,
         1
       ) AS value
FROM   dual
CONNECT BY REGEXP_COUNT(
         'Data 1__##__Data Two__##__Third Data__##__4th Data__##__', 
         '(.*?)__##__'
       ) >= LEVEL;


VALUE


Data 1

Data Two

Third Data

4th Data