DB2 - String operations - db2

Question

Can we check a string value with comma separated exists in another comma separated string in DB2?
I have say two string like below
Case-1:
String-1:'ABC,XYZ,PQR'
Srting-2:'MNO,PQR'
I want to have any function in DB2 which should return 1 in the above case as PQR from String-2 exists in String-1. The value should match any string within comma or after or before comma.
Case-2:
String-1:'ABC,XYZ,PQR'
Srting-2:'MNO,P QR'
But for the above case the same function should return 0. As there is space after "P"
I also want to have a similar function which should return the concatenated string but removes duplicates.
Case-1:
String-1:'ABC,XYZ,PQR'
Srting-2:'MNO,PQR'
Output should be 'ABC,XYZ,PQR,MNO' .
The order in comma separated values doesn't matter in this case; but PQR should not be repeated twice.
Case-2:
String-1:'ABC,XYZ,PQR'
Srting-2:'MNO,P QR'
In this case output should be 'ABC,XYZ,PQR,MNO,P QR' .
I am trying to achieve this using SQL or any function in DB2.
There is another case where I want to remove matching part of the string
Case-3:
String-1:'ABC,XYZ,PQR'
Srting-2:'MNO,PQR'
Output should be 'ABC,XYZ,MNO'
Obviously String-1 and String-2 can have any number of values separated by comma.

Answer 1

Try this:
CREATE FUNCTION SPLITTER (P_STR VARCHAR(4000), P_DELIM VARCHAR(10))
RETURNS TABLE (SEQ INT, TOKEN VARCHAR(50))
RETURN
SELECT TOK.SEQ, TOK.TOKEN
FROM XMLTABLE
(
'for $id in tokenize($s, $t) return <i>{string($id)}</i>' PASSING P_STR AS "s", P_DELIM AS "t"
COLUMNS
SEQ FOR ORDINALITY
, TOKEN VARCHAR(50) PATH '.'
) TOK;
SELECT
CASE
WHEN EXISTS
(
SELECT 1
FROM TABLE (SPLITTER ('ABC,XYZ,PQR', ',')) A
JOIN TABLE (SPLITTER ('MNO,PQR', ',')) B ON B.TOKEN = A.TOKEN
)
THEN 1
ELSE 0
END
FROM SYSIBM.SYSDUMMY1;
SELECT LISTAGG (TOKEN, ',')
FROM
(
SELECT TOKEN
FROM TABLE (SPLITTER ('ABC,XYZ,PQR', ','))
UNION
SELECT TOKEN
FROM TABLE (SPLITTER ('MNO,PQR', ','))
);
SELECT LISTAGG (TOKEN, ',')
FROM
(
SELECT DISTINCT COALESCE (A.TOKEN, B.TOKEN) AS TOKEN
FROM TABLE (SPLITTER ('ABC,XYZ,PQR', ',')) A
FULL JOIN TABLE (SPLITTER ('MNO,PQR', ',')) B ON B.TOKEN = A.TOKEN
WHERE A.TOKEN IS NULL OR B.TOKEN IS NULL
);
dbfiddle link.