创建测试用表：
CREATE OR REPLACE VIEW v AS SELECT ‘好好学习‘ AS c FROM DUAL; SELECT * FROM v;
sql代码如下：
SELECT SUBSTR(c, LEVEL, 1) AS c FROM v CONNECT BY LEVEL <= LENGTH(c);
执行结果如下：
遍历字符串
原文：http://www.cnblogs.com/minisculestep/p/4889658.html
