oracle substr小实例

问题：

有如下字符串
,aa,,cc,dd
我需要弄成
1 aa
2 null
3 cc
4 dd

解法：

SQL> SELECT id,
2 NVL(SUBSTR(
3 col1,
4 INSTR(col1,',',1,id)+1,
5 INSTR(col1,',',1,id+1)-INSTR(col1,',',1,id)-1
6 ),'null') AS res
7 FROM
8 (
9 WITH t AS
10 (
11 SELECT ',aa,,cc,dd'||',' as col1
12 FROM dual
13 )
14 SELECT col1,
15 LEVEL id
16 FROM t
17 CONNECT BY LEVEL<=LENGTH(col1)-
18 LENGTH(REPLACE(col1,','))
19 -1
20 );

ID RES
---------- ----------------------
1 aa
2 null
3 cc
4 dd

原帖：http://www.itpub.net/thread-1407258-1-1.html