该“在线点歌系统”只是对数据库应用技术的一个样本数据库的实例，重在对数据库的一些方法的熟悉和建立，其中我们从数据库的概念模型到把理论付诸实际，设计数据库，找出关系模式绘制ER图，再到应用SQL语言对数据库的建立，再到数据的输入，最后完成一些关系运算表达式的表达和SELECT查询语句的使用。-The " online VOD system"　is just a sample of the database instance database application technology, focusing on some of the ways to build a database of familiar and which we conceptual model from the database to put theory into practice, designing a database to identify Draw relational schema ER diagram, and then use the SQL language to the database is established, then the input data, and finally completed using some relational operator expression expression and SELECT query statement.