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 ||
(row_number() over(PARTITION BY it.customer ORDER BY
it.customer)) a,
it.customer ||
(row_number() over(PARTITION BY it.customer ORDER BY
it.customer) - 1) b,
it.*
FROM invoice_test it
ORDER BY it.customer) tt
CONNECT BY PRIOR a = b) yy;

应该有点问题关于是否可用rownum?

答案是否。why?

因为把 row_number() over(PARTITION BY it.customer ORDER BY it.customer) 改为 rownum 的话，那么connect by 就无法通过父子结构去遍历数据。rownum它是伪列，它是按照当初创建表时数据插入的顺序生成的。

以下是用rownum产生的结果:

SQL> SELECT
2 it.customer||rownum c,
3 it.customer ||(rownum-1) p,
4 customer,
5 order_num
6 FROM
7 invoice_test it
8 order by customer
9 ;

C P CUSTOMER ORDER_NUM
------------------------------------------------------------ ------------------------------------------------------------ -------------------- ---------
A1 A0 A 263663
A2 A1 A 273631
A5 A4 A 553024
B3 B2 B 163263
B4 B3 B 173636

ths...