................................................72.2.2指导老师管理模块...........................................................................................................82.2.3学生选题模块...................................................................................................................82.2.4选题流程...........................................................................................................................92.5数据分析............................................................................................................................9第三章数据库设计........................................................103.1数据库选择......................................................................................................................103.2数据库的完整性约束......................................................................................................113.3数据库的安全性..............................................................................................................133.4数据库的概念结构设计..................................................................................................143.4.1实体与属性之间的关系................................................................................................143.4.2数据库的E-R图............................................................................................................153.5数据库逻辑结构设计.......................................................................................................16第四章系统设计..........................................................184.1系统总体设计...................................................................................................................184.2公用模块的编写...............................................................................................................204.2.1数据库连接文件.............................................................................................................204.2.2用户登录和注销...........................................................................................................