mag@itloaner1_local > SELECT * FROM EMP;

     EMPNO ENAME      JOB              MGR HIREDATE         SAL       COMM     DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
      7369 SMITH      CLERK           7902 17-DEC-80        800                    20
      7499 ALLEN      SALESMAN        7698 20-FEB-81       1600        300         30
      7521 WARD       SALESMAN        7698 22-FEB-81       1250        500         30
      7566 JONES      MANAGER         7839 02-APR-81       2975                    20
      7654 MARTIN     SALESMAN        7698 28-SEP-81       1250       1400         30
      7698 BLAKE      MANAGER         7839 01-MAY-81       2850                    30
      7782 CLARK      MANAGER         7839 09-JUN-81       2450                    10
      7788 SCOTT      ANALYST         7566 13-JUL-87       3000                    20
      7839 KING       PRESIDENT            17-NOV-81       5000                    10
      7844 TURNER     SALESMAN        7698 08-SEP-81       1500          0         30
      7876 ADAMS      CLERK           7788 13-JUL-87       1100                    20
      7900 JAMES      CLERK           7698 03-DEC-81        950                    30
      7902 FORD       ANALYST         7566 03-DEC-81       3000                    20
      7934 MILLER     CLERK           7782 23-JAN-82       1300                    10

14 rows selected.

mag@itloaner1_local > CREATE OR REPLACE function fOO (cin in varchar2 ) return
  2  varchar2 is
  3  retval varchar2(200);
  4  cursor c1 is select ENAME  from emp WHERE JOB=CIN;
  5  begin
  6  for crec in c1 loop
  7  if c1%rowcount=1 then
  8  retval:= crec.ENAME;
  9  else
 10  retval:=retval||','||crec.ENAME;
 11  end if;
 12  end loop;
 13  return retval;
 14  end;
 15  /

Function created.

mag@itloaner1_local > SELECT DISTINCT JOB,FOO(JOB) FROM EMP;

JOB       FOO(JOB)
--------- ----------------------------------------
ANALYST   SCOTT,FORD
CLERK     SMITH,ADAMS,JAMES,MILLER
MANAGER   JONES,BLAKE,CLARK
PRESIDENT KING
SALESMAN  ALLEN,WARD,MARTIN,TURNER