with t1(c1,c2) as (values
('지점A', 5),
('총무부',12),
('지점C', 2),
('지점D', 2),
('지점B', 3),
('E',1),
('BB',1),
('GG',1)),
t2(ca) as (values (1),(2))

select case when rk<6 and ca=1 then rk else cast(null as int) end rk,
       case when rk<6 and ca=1 then c1     
            when rk>5 and ca=1 then '기타'
            when ca=2 then '계' end c1,
       sum(c2) c2, int(dec(sum(c2))/max(sm)*100) pct
 from (
select c1,c2,rownumber() over(order by c2 desc) rk,sum(c2) over() sm from t1
      ) t1 , t2
group by case when rk<6 and ca=1 then rk else cast(null as int) end,
         case when rk<6 and ca=1 then c1    
              when rk>5 and ca=1 then '기타'
              when ca=2 then '계' end;
~

RK                   C1     C2          PCT       
-------------------- ------ ----------- -----------
                   1 총무부          12          44
                   2 지점A            5          18
                   3 지점B            3          11
                   4 지점C            2           7
                   5 지점D            2           7
                   - 기타             3          11
                   - 계              27         100

select case when rnk <6 then rnk else cast(null as int) end rnk,
 case when rnk<6 then uname else '기타' end uname,sum(cnt) cnt

          from (select uname, cnt, rank() over(order by cnt desc) rnk
                  from (select c.uname, count(*) as cnt
 from mrole_entrust a, userinfo_temp b,mcodedesc c
 where b.employeenumber = a.fromuser and b.brnchofficcd = c.uuid and mcode_uuid = 101
 and  startdate between '20080610' and '20080620'
 group by c.uname) a) b
 group by case when rnk<6 then rnk else cast(null as int) end, case when rnk<6 then uname else '기타' end;


답변주신대로 응용해서 짜보았습니다 잘되네요 ^^ 감사합니다.
하나더 질문,... 백문율도 구해야되는데 어떻게 구해야될까요....
점점더 막막해지네요~

고수님들 지나가지마시고 댓글한번 ^^

1. 소숫점 첫째짜리까지 표기

 dec(dec(sum(c2))/max(sm)*100,4,1) pct