DBS软件A卷预.docVIP

哈尔滨理工大学 2008－2009学年第一学期考试试题　 　　 A卷 2009年 1月7日 第  PAGE 4 页 共  NUMPAGES 5 页 软件学院、软件工程系 出题教师：崔香、刘欢 系主任： 第  PAGE 5 页 共  NUMPAGES 5 页 装 订 线 班级： 学号： 姓名： 考试科目: 数据库系统(双语) 考试时间: 120分钟 试卷总分: 100分 考试班级：软件07-1、2、3、4、5、6班 题号IIIIIIIV总分得分评卷教师Blank-filling questions. (2 marks × 10 = 20 marks) Given two original values A=1000, B=2000; compute both the values of A and B after the transactions T1 and T2 with the right side schedule. A= ; B= . The three basic steps in query processing include: parsing and translation, __________ and . In physical level, the database is stored as a collection of , each of which is a sequence of records. In parallel database systems, a parallel machine consists of a small number of powerful processors. There are two classical approaches to ensure atomicity despite failures which are log-based recovery and . A ________ of an entity set is a set of one or more attributes whose values uniquely determine each entity. Two relational algebra expressions are said to be if on every legal database instance the two expressions generate the same set of tuples. To design a trigger mechanism, we must specify the under which the trigger is to be executed; then specify the actions to be taken when the trigger executes. Briefly description questions. (30 marks） What is the purpose of the index mechanism in database system? And give the definitions of primary index and secondary index. (5 marks) List the advantages of using Database System to store data. (5 marks) Compute the closure of the following set F of functional dependencies for relation schema R = (A, B, C, D, E). F ={A →BC, CD →E, B → D, E → A }, list the candidate keys for R. (5 marks) compute the canonical cover Fc. (5 marks) Compute the two relational algebra expressions