[]数据合并的有关问题，高手请帮忙

[求助]数据合并的问题，高手请帮忙！
示例如下，表A：

订单号         客户
263663         A
273631         A
163263         B
173636         B

想得到这样的结果：

客户             订单号
A                   263663;273631
B                   163263;173636

请问这个要怎么样才做得到呢，请各位高手赐教。

------解决方案--------------------
你也有够懒得了，我的不是中文系统，没法用中文，你看懂意思就自己试下阿。。。
SELECT
distinct 客户
, ltrim(first_value(a) over (partition by 客户 order BY lev DESC) , '; ') 订单号
FROM
(SELECT
客户
, 订单号
, LEVEL lev
, sys_connect_by_path(订单号, '; ') a
FROM
(SELECT
temp5.客户||ROWNUM c
, (temp5.客户 ||( ROWNUM - 1)) p
, 客户
, 订单号
FROM
temp5)
CONNECT BY
PRIOR c = p)

------解决方案--------------------
drop table invoice ;

create table invoice(order_num number(6),customer varchar2(20));

insert into invoice values (263663, 'A ');
insert into invoice values (273631, 'A ');
insert into invoice values (163263, 'B ');
insert into invoice values (173636, 'B ');

select customer,order_num from invoice;

SELECT
distinct customer,
ltrim(first_value(a) over (partition by customer order BY lev DESC) , '; ') order_num
FROM
(SELECT
customer,
order_num,
LEVEL lev,
sys_connect_by_path(order_num, '; ') a
FROM
(SELECT
invoice.customer||ROWNUM c,
(invoice.customer ||( ROWNUM - 1)) p,
customer,
order_num
FROM
invoice)
CONNECT BY
PRIOR c = p)