如：
create table ttt
(
o number,
n varchar2(22)
);
create table sub_ttt
(
nn varchar2(33),
fo number
);
insert into ttt values(1,'aaa');
insert into sub_ttt values('sub1',1);
insert into sub_ttt values('sub2',1);
insert into sub_ttt values('sub3',1);
SQL> select t1.o,t1.n ,t2.nn
2 from
3 ttt t1,sub_ttt t2 where t1.o=t2.fo order by 3;
O N NN
---------- ---------------------- ---------------------------------
1 aaa sub1
1 aaa sub2
1 aaa sub3
我现在想这样显示，请教下怎么写：
O N NN
---------- ---------------------- ---------------------------------
1 aaa sub1
sub2
sub3
