create table wlbtest1(
   username varchar2(2),
   deptID number
);

create table wlbtest2(
   deptName varchar2(10),
   deptID number
);

insert into wlbtest1 values ('a', 1);
insert into wlbtest1 values ('b', 1);
insert into wlbtest1 values ('c', 1);
insert into wlbtest1 values ('d', 2);
insert into wlbtest1 values ('e', 2);
insert into wlbtest1 values ('f', 2);
insert into wlbtest2 values ( '部门1' ,1);
insert into wlbtest2 values ( '部门2', 2);

select deptID, wm_concat(username) username,'部门'||deptID deptName from wlbtest1 group by deptID 

执行结果：