--------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

学习笔记之SQL