oracle sql 分组求最大值后，要显示其它列
select
t_a.a,t_a.b,max(t_a.c) c,
?
MAX (t_a.d)KEEP (DENSE_RANK FIRST????? ORDER BY t_a.c _ DESC)? d_
from t_a
group by
t_a.a,t_a.b
