Oracle REGEXP_SUBSTR returning NULL as value - sql

Question

I am trying to split data from a column into rows but I am facing this issue here.
When i run this query it splits the data fine but it is also returning NULL as an extra row too.
Here is the value I am trying to split ,162662163,90133140,163268955,169223426,169222899,
WITH CTE AS(
SELECT
RTRIM(LTRIM(PG2.MULTILIST11, ','), ',') ACCESS_BY_GROUPS
FROM AGILE.ITEM I
INNER JOIN AGILE.PAGE_TWO PG2 ON PG2.ID = I.ID
WHERE
ITEM_NUMBER IN --('313-000074',
('313-000090')
)
SELECT DISTINCT
REGEXP_SUBSTR(ACCESS_BY_GROUPS, '[^,]+', 1, column_value) ACCESS_BY_GROUPS
FROM CTE
CROSS JOIN TABLE(CAST(MULTISET(SELECT LEVEL FROM DUAL
CONNECT BY LEVEL <= REGEXP_COUNT(CTE.ACCESS_BY_GROUPS, ',') + 10
) AS sys.odcinumberlist))
I don't want to get that null value. I cannot apply that check out of the query because it will affect other column values too so I want it to be handled somewhere in the function. I hope someone can help.

Answer 1

It is because of leading and trailing commas.
One option is to begin from position 2 (see line #3) and limit number of values (line #5)
SQL> with test (col) as
2 (select ',162662163,90133140,163268955,169223426,169222899,' from dual)
3 select regexp_substr(col, '[^,]+', 2, level) res
4 from test
5 connect by level <= regexp_count(col, ',') - 1
6 /
RES
-------------------------------------------------
162662163
90133140
163268955
169223426
169222899
SQL>
Another is to remove leading and trailing comma first, and then split the rest into rows:
SQL> with test (col) as
2 (select ',162662163,90133140,163268955,169223426,169222899,' from dual),
3 temp as
4 -- remove leading and trailing comma first
5 (select ltrim(rtrim(col, ','), ',') col
6 from test
7 )
8 select regexp_substr(col, '[^,]+', 1, level) res
9 from temp
10 connect by level <= regexp_count(col, ',') + 1;
RES
------------------------------------------------
162662163
90133140
163268955
169223426
169222899
SQL>
[EDIT - for more than a single row]
If there are more rows involved, code has to be changed. Note that there must be some kind of a unique identifier for every row (ID in my example).
SQL> with test (id, col) as
2 (select 1, ',162662163,90133140,163268955,169223426,169222899,' from dual union all
3 select 2, ',1452761,1452762,' from dual
4 )
5 select id,
6 regexp_substr(col, '[^,]+', 2, column_value) res
7 from test cross join table(cast(multiset(select level from dual
8 connect by level <= regexp_count(col, ',') - 1
9 ) as sys.odcinumberlist))
10 order by id, column_value
11 /
ID RES
---------- -------------------------------------------------
1 162662163
1 90133140
1 163268955
1 169223426
1 169222899
2 1452761
2 1452762
7 rows selected.
SQL>