LISTAGG( [ ALL ] [ DISTINCT ] measure_expr [, 'delimiter'] [listagg_overflow_clause] )
  [ WITHIN GROUP ] (order_by_clause) [OVER query_partition_clause]

select listagg(unique to_char(mod(level, 3)), ',') within group (order by null) v193
from dual
connect by level<=10;

V193   
-----
0,1,2

select listagg(unique job, ',') within group (order by null)
from emp 
group by deptnoORA-30482: DISTINCT option not allowed for this function

ORA-30482: DISTINCT option not allowed for this function

select listagg(job, ',') --within group (order by null)
from emp 
group by deptno

MANAGER,SALESMAN,SALESMAN,SALESMAN,SALESMAN,CLERK
PRESIDENT,MANAGER,CLERK
MANAGER,ANALYST,ANALYST,CLERK,CLERK

select listagg(job, ',')  l
from emp 
group by deptno

MANAGER,SALESMAN,SALESMAN,SALESMAN,SALESMAN,CLERK
PRESIDENT,MANAGER,CLERK
MANAGER,ANALYST,ANALYST,CLERK,CLERK

     EMPNO ENAME      JOB              MGR HIREDATE        SAL       COMM     DEPTNO
---------- ---------- --------- ---------- -------- ---------- ---------- ----------
      7782 CLARK      MANAGER         7839 09.06.81       2450                    10
      7839 KING       PRESIDENT            17.11.81       5000                    10
      7934 MILLER     CLERK           7782 23.01.82       1300                    10
      7566 JONES      MANAGER         7839 02.04.81       2975                    20
      7902 FORD       ANALYST         7566 03.12.81       3000                    20
      7876 ADAMS      CLERK           7788 12.01.83       1100                    20
      7369 SMITH      CLERK           7902 17.12.80        800                    20
      7788 SCOTT      ANALYST         7566 09.12.82       3000                    20
      7521 WARD       SALESMAN        7698 22.02.81       1250        500         30
      7844 TURNER     SALESMAN        7698 08.09.81       1500                    30
      7499 ALLEN      SALESMAN        7698 20.02.81       1600        300         30
      7900 JAMES      CLERK           7698 03.12.81        950                    30
      7698 BLAKE      MANAGER         7839 01.05.81       2850                    30
      7654 MARTIN     SALESMAN        7698 28.09.81       1250       1400         30

результат

    DEPTNO F
---------- --------------------------------------------------
        30 BLAKE,MARTIN,ALLEN,WARD,TURNER,JAMES
        20 SCOTT,FORD,JONES,ADAMS,SMITH
        10 KING,CLARK,MILLER

select loc_u_loc, list (loc_u_code order by loc_u_level desc, loc_u_code) a
from loc_user
group by loc_u_loc
order by loc_u_loc desc

SQL> select deptno
  2  ,listagg(ename,',') WITHIN GROUP (ORDER BY sal+nvl(comm,0) desc,empno) f
  3  from emp e
  4  group by deptno
  5  order by deptno desc
  6  /

    DEPTNO F
---------- --------------------------------------------------
        30 BLAKE,MARTIN,ALLEN,WARD,TURNER,JAMES
        20 SCOTT,FORD,JONES,ADAMS,SMITH
        10 KING,CLARK,MILLER

select loc_u_loc, list (a) from (
select loc_u_loc, loc_u_level, list (loc_u_code) a
from loc_user
group by loc_u_loc, loc_u_level
order by loc_u_loc desc, loc_u_level desc) z
group by loc_u_loc
order by loc_u_loc desc