select created_by, translate(ltrim(text, '/'), '*/', '*,') researcherlist
  from (select row_number() over(partition by created_by order by created_by, lvl desc) rn,
               created_by,
               text
          from (select created_by,
                       level lvl,
                       sys_connect_by_path(c_researcher_code, '/') text
                  from (select created_by,
                               user_name as c_researcher_code,
                               row_number() over(partition by created_by order by created_by, user_name) x
                          from fnd_user
                         order by created_by, user_name) a
                connect by created_by = prior created_by
                       and x – 1 = prior x))
 where rn = 1
 order by created_by;

SQL分析：

1、利用 “ROW_NUMBER () OVER (PARTITION BY……” 为按“创建人”汇总后的数据行添加组内序号

2、“SYS_CONNECT_BY_PATH”  按组内序号相邻关系，为每一层进行不同行的“名称”叠加

3、再次利用“创建人”进行组内分组，但按第二部中的层次排倒序，增加调整后等级

4、取所有调整后等级为1的结果，即为所要求的数据行

其他参考：http://www.ningoo.net/html/2008/how_to_do_string_aggregate_on_oracle.html