Recipients
------------
R23198U,R324I98

Recipients
------------
Lonnie Lawson, Stan Smith

SELECT (SELECT Listagg(full_name, ',')
             within GROUP(ORDER BY full_name) AS CC_Recipients
    FROM   (SELECT first_name
                   ||' '
                   ||last_name AS full_name
            FROM   users_table
            WHERE  user_name IN (SELECT DISTINCT Trim(Regexp_substr(
                                cc_recipients,
                                '[^,]+', 1,
                                                     LEVEL))
                                 FROM   dual
                                 CONNECT BY Regexp_substr(
                                            cc_recipients,
                                            '[^,]+', 1,
                                            LEVEL) IS
                                            NOT NULL))t) AS cc_rec
FROM   email_queue
WHERE  cc_recipients IS NOT NULL;

CC_REC                      CC_RECIPIENTS
Lonnie Lawson,Stan Smith    R23198U,R324I98
Lonnie Lawson,Stan Smith    R23198U
Lonnie Lawson,Stan Smith    R23198U
Lonnie Lawson,Stan Smith    R23198U