--------参考网站--------
http://en.wikipedia.org/wiki/SQL
SQL@Wiki
http://en.wikipedia.org/wiki/Delete_%28SQL%29
Delete (SQL)@Wiki
http://en.wikipedia.org/wiki/Insert_%28SQL%29
Insert (SQL)@Wiki
http://www.cnblogs.com/diction/archive/2008/01/18/1043844.html
in和exists的区别与SQL执行效率分析
原文：http://www.cnblogs.com/pegasus923/p/1954146.html