Oracle 数据合并的解决办法(用connect by 树解决)

首先来说说问题的需求: (是csdn论坛里的问题) 

示例如下，表invoice_test：

order_num   customer
263663               A
273631               A
163263               B
173636               B
553024               A

想得到这样的结果：

customer      order_num
A         263663;273631;553024
B         163263;173636

SQL:

     SELECT DISTINCT yy.customer,
                     ltrim(first_value(path)
                           over(PARTITION BY yy.customer ORDER BY yy.lev DESC),
                           ';') order_num
       FROM (SELECT tt.*,
                    LEVEL lev,
                    sys_connect_by_path(order_num, ';') path
               FROM (SELECT it.customer ||