Concatenate using SQL rather than Oracle functions Oracle 8i

Question

Is it possible to concatenate field values using SQL alone and not an Oracle function
For the following dataset I would like the results to be the following
1 User_lastname1 2,7
2 User_lastname2 2,7
3 User_lastname3 2
4 User_lastname4 7
CREATE TABLE users
( user_id NUMBER(10)
, user_lastname VARCHAR2 (50)
, workgroup NUMBER(10)
INSERT ALL
INTO users(user_id, user_lastname, workgroup) VALUES (1, User_lastname1, 2)
INTO users(user_id, user_lastname, workgroup) VALUES (1, User_lastname1, 7)
INTO users(user_id, user_lastname, workgroup) VALUES (2, User_lastname2, 2)
INTO users(user_id, user_lastname, workgroup) VALUES (2, User_lastname2, 7)
INTO users(user_id, user_lastname, workgroup) VALUES (3, User_lastname3, 2)
INTO users(user_id, user_lastname, workgroup) VALUES (4, User_lastname4, 7)

Answer 1

Maybe (provided a user is not a member of more than six workgroups)
select user_id,
       user_lastname,
       max(decode(rno,1,workgroup,null)) || max(decode(rno,2,','||workgroup,null)) ||
                                            max(decode(rno,3,','||workgroup,null)) ||
                                            max(decode(rno,4,','||workgroup,null)) ||
                                            max(decode(rno,5,','||workgroup,null)) ||
                                            max(decode(rno,6,','||workgroup,null)) string
  from (select user_id,
               user_lastname,
               workgroup,
               row_number() over (partition by user_id,user_lastname order by workgroup) rno
          from users
group by user_id,
          user_lastname
order by user_id,
          user_lastnameor (provided a user is not a member of more than five workgroups)
select user_id,
       user_lastname,
       string
  from (select user_id,
               user_lastname,
               row_number() over (partition by user_id,user_lastname order by workgroup) rno,
               workgroup || lead(','||workgroup,1) over (partition by user_id,user_lastname order by workgroup) ||
                            lead(','||workgroup,2) over (partition by user_id,user_lastname order by workgroup) ||
                            lead(','||workgroup,3) over (partition by user_id,user_lastname order by workgroup) ||
                            lead(','||workgroup,4) over (partition by user_id,user_lastname order by workgroup) string
          from users
where rno = 1
order by user_id,
          user_lastnameRegards
Etbin