说明：用JSP+MySQL数据库创建留言本，首先要创建MySQL数据库，关于MySQL的使用请到 http://pinghui.51.net/download/012mysql.chm 下载教程。现在为了说明的需要，我们假设数据库已经建立完成，数据库的名称是pinghui，其中有comment表是记录留言信息的。
数据库的结构为：
+-----------+-------------+------+-----+---------------------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-----------+-------------+------+-----+---------------------+----------------+
| userid | int(11) | | PRI | 0 | auto_increment |
| username | char(20) | | | | |
| sex | char(2) | | | | |
| address | char(40) | YES | | NULL | |
| ip | char(15) | | | | |
| post | int(11) | YES | | 0 | |
| oicq | int(11) | YES | | 0 | |
| icq | int(11) | YES | | 0 | |
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