Loop over a each value wrapped up by listagg

I have a table with a column named column_names and for each row it has a list of column names separated by a comma, for example:

I want to iterate over each named string in column names, here is what I have tried:

DECLARE
  deposits VARCHAR(255);
BEGIN
   FOR DEPO IN ( SELECT REGEXP_SUBSTR (
   column_names, '[^,]+') "REGEXPR_SUBSTR" INTO deposits
 FROM REFERENCE_TEST )
   LOOP
      DBMS_OUTPUT.PUT_LINE (DEPO.deposits);
   END LOOP;
END;

I used DECLARE because I kept getting an error that DEPO was not declaring something.

The error I get:

Error report -
ORA-06550: line 8, column 34:
PLS-00302: component 'DEPOSITS' must be declared
ORA-06550: line 8, column 7:
PL/SQL: Statement ignored
06550. 00000 -  "line %s, column %s:\n%s"
*Cause:    Usually a PL/SQL compilation error.
*Action:

>Solution :

Don’t use SELECT ... INTO ... inside a cursor:

BEGIN
   FOR DEPO IN (
     SELECT REGEXP_SUBSTR (column_names, '[^,]+') AS REGEXPR_SUBSTR
     FROM   REFERENCE_TEST
   )
   LOOP
      DBMS_OUTPUT.PUT_LINE (DEPO.REGEXPR_SUBSTR);
   END LOOP;
END;
/

Which will get you the first value in each row.

So, for the sample data:

CREATE TABLE REFERENCE_TEST ("TABLE", column_names) AS
SELECT 'some', 'DEPOSITS_COUNT,DEPOSITS' FROM DUAL UNION ALL
SELECT 'numbers', 'ONE,TWO,THREE' FROM DUAL;

It outputs:

DEPOSITS_COUNT
ONE

If you want all the values then you need to use a row-generator and split the string. You can do that using a recursive sub-query factoring clause and simple string functions (which is much faster than regular expressions):

BEGIN
   FOR DEPO IN (
     WITH bounds (column_names, spos, epos) AS (
       SELECT column_names,
              1,
              INSTR(column_names, ',', 1)
       FROM   reference_test
     UNION ALL
       SELECT column_names,
              epos + 1,
              INSTR(column_names, ',', epos + 1)
       FROM   bounds
       WHERE  epos > 0
     )
     SEARCH DEPTH FIRST BY column_names SET order_id
     SELECT CASE epos
            WHEN 0
            THEN SUBSTR(column_names, spos)
            ELSE SUBSTR(column_names, spos, epos - spos)
            END AS name
     FROM   bounds
   )
   LOOP
      DBMS_OUTPUT.PUT_LINE (DEPO.name);
   END LOOP;
END;
/

Which outputs:

DEPOSITS_COUNT
DEPOSITS
ONE
TWO
THREE

fiddle