上海财经大学数据库系统课程考试卷(A).doc

上海财经大学《数据库系统》课程考试卷（A） 2005——2006学年 第二学期 姓名 学号 班级 得分 True or False. (20 points) External/Conceptual Mapping is the key to physical data independence. DA is the person who provides the necessary technical support for implementing those decisions. It is the job of the DML processor to choose an efficient way to implement user’s request. Relational data model represents the data in a database as a collection of tables. Indexes allow the database management system to directly access the rows of the table on which the index has been defined. Since the logical data structures are intended for the application programmers, the database designer is not involved in their development. Views are only descriptions of data. They are not real tables. Denormalization causes the redundant storage of information. Horizontal splitting of a relational variable always creates relational variables for different primary key ranges of the original relational variable. For an unordered retrieval request, different executions of the request may return the retrieved rows in a different sequence. A relationship type can again be the source or target of a relationship type. A business relationship type can always be translated into a relationship type of the entity-relationship model for the application domain. The updating of redundant information for violations of the Third Normal Form cannot be controlled by triggers. SQL does not permit users to define their own types, columns must be defined in terms of built-in types only. Once a transaction commits, its updates may not survive in the database when there is a subsequent system crash. Any transaction which was in progress at the time of the system failure must be redo at restart time. The checkpoint record gives a list of all transactions that were in progress at the time the checkpoint was taken. If transaction A holds an S lock on tuple t, then a request from some distinct transaction B for a X lo