create table test(a int,b int,c int)

insert test

select 1,2,1 union all

select 1,2,2 union all

select 1,2,3 union all

select 1,2,4 union all

select 1,3,5 union all

select 1,4,6 union all

select 1,5,7 union all

select 1,4,8 union all

select 1,5,9 union all

select 1,2,3

-------------------------------------

select a,b,max(c) c

  from test

 group by a,b

 order by c desc

/*

a           b           c

----------- ----------- -----------

1           5           9

1           4           8

1           3           5

1           2           4

(4개 행 적용됨)

*/