原帖:
http://topic.youkuaiyun.com/u/20110511/17/22dcbc7b-e8d1-4c77-a4de-1ecca939fb24.html?50950
oracle nullif()函数
http://www.techonthenet.com/oracle/functions/nullif.php
oracle lag()分析函数:
http://blog.youkuaiyun.com/BOBO12082119/archive/2011/03/30/6289648.aspx
oracle row_number()分析函数:
http://blog.youkuaiyun.com/BOBO12082119/archive/2011/04/01/6294889.aspx