select deptno,
       max(sal) as max_sal,
       max(ename) keep(dense_rank first order by sal desc) as max_ename,
       sum(sal) keep(dense_rank first order by sal desc) as sum_ename,
       count(sal) keep(dense_rank first order by sal desc) as count_ename,
       to_char(wm_concat(ename) keep(dense_rank first order by sal desc)) as enames
from emp
group by deptno;

SCOTT@orcl_12.1.0.2.0> column enames format a10
SCOTT@orcl_12.1.0.2.0> select deptno,
  2  	    max (sal) as max_sal,
  3  	    max (ename) as max_ename,
  4  	    sum (sal) as sum_ename,
  5  	    count (sal) as count_ename,
  6  	    listagg (ename, ',') within group (order by ename) as enames
  7  from   (select deptno, sal, ename,
  8  		    dense_rank () over (partition by deptno order by sal desc) as dr
  9  	     from   emp)
 10  where  dr = 1
 11  group  by deptno
 12  order  by deptno;

    DEPTNO    MAX_SAL MAX_ENAME   SUM_ENAME COUNT_ENAME ENAMES
---------- ---------- ---------- ---------- ----------- ----------
        10       5000 KING             5000           1 KING
        20       3000 SCOTT            6000           2 FORD,SCOTT
        30       2850 BLAKE            2850           1 BLAKE

3 rows selected.