关于oracle函数listagg的使用说明

WITH TMP AS
(SELECT TU.USERNAME, TE.EMP_NAME, TE.EMP_DUTY_NAME, TR.ROLE_NAME
FROM TS_USER       TU,
TS_USER_ROLE  TUR,
TS_ROLE       TR,
TM_DEPARTMENT TD,
TM_EMPLOYEE   TE
WHERE TU.USER_ID = TUR.USER_ID
AND TU.EMP_ID = TE.EMP_ID
AND TUR.ROLE_ID = TR.ROLE_ID
AND TU.DEPT_ID = TD.DEPT_ID
AND TD.DEPT_CODE = '755Y'
ORDER BY TU.USERNAME ASC)
SELECT USERNAME 用户名,
EMP_NAME 员工姓名,
EMP_DUTY_NAME 职位,
LISTAGG(ROLE_NAME, ',') WITHIN GROUP(ORDER BY ROLE_NAME) 用户角色
FROM TMP
GROUP BY USERNAME, EMP_NAME, EMP_DUTY_NAME;