里面包含数据定义与简单查询实验、表的连接和嵌套查询实验、表的集合查询与统计实验、视图与数据控制实验、数据库的建立和维护实验-Which contains the data definition and a simple query test, the connection table and nested queries experiment, a collection of query statistics table test, view and control of experimental data, database creation and maintenance of experimental