Instead of Stragg /// Allow Duplicate

SELECT
deptno,
LTRIM(SYS_CONNECT_BY_PATH(ename, ','), ',') employees
FROM (
SELECT deptno,
ename,
row_number() over(PARTITION BY deptno ORDER BY deptno) rnum,
count(*) over(PARTITION BY deptno) tot
FROM scott.emp
)
WHERE rnum=tot
START WITH rnum = 1
CONNECT BY PRIOR rnum = rnum -1 AND PRIOR deptno = deptno;


select tb.deptno , substr ( sys_connect_by_path( tb.EMPNO, ',' ) , 2) as string
from ( select deptno ,EMPNO ,row_number() over ( partition by deptno
order by EMPNO ) as val_index from
scott.emp WHERE EMPNO IS NOT NULL ) tb where
connect_by_isleaf = 1 connect by val_index = prior val_index + 1 and
deptno = prior deptno start with val_index = 1 ;


WITH tab AS
(
SELECT &strg str
FROM DUAL)
SELECT REGEXP_SUBSTR (str, '[^,]+', 1, LEVEL) RESULT
FROM tab
CONNECT BY LEVEL <=
((SELECT SUM (CASE
WHEN SUBSTR (str, LEVEL, 1) = ','
THEN 1
WHEN LENGTH (str) = LEVEL
THEN 1
ELSE 0
END
)
FROM tab
CONNECT BY LEVEL <= LENGTH (str)));


SELECT REPLACE(&strg ,',',CHR(13)) FROM DUAL;


FROM 10G ONWARDS

SELECT deptno,wmsys.wm_concat(ename) d
FROM scott.emp group BY deptno

------------------------------------------
To remove duplicate  from a SQL

SELECT JOB, ENAME FROM
(SELECT DISTINCT ENAME,JOB, row_number () OVER (PARTITION BY ENAME ORDER BY ENAME) rn
FROM scott.emp )
WHERE rn = 1