数据库试题答案 英文卷.doc

哈尔滨理工大学20062007学年第一学期考试试题答案 A卷装 订 线班级： 学号： 姓名：考试科目： 数据库系统 考试时间：120分钟 试卷总分100分考试班级：题号一二三四五六七八九十总分得分评卷教师I、Choice Questions1.B 2.C 3.D 4.B 5.D6.C 7.D 8.D 9.B 10.CII、 Blank-filling Questions. 1、 condition(s) , action(s) 2、A= 180 ;B= 170 3、 logical , view or view ， logical 4、 4ms 5、 optimizer evaluation engine III、 Answer the following questions briefly. 1、A superkey is a set of one or more attributes that, taken collectively, to identify uniquely an entity in the entity set. Candidate keys are minimal superkeys which no proper subset is a superkey. Primary key is a candidate key that is chosen as the principal means of identifying entities within an entity set.2、Database administrators duties include: (choose any four from the following)l Schema definitionl Storage structure and access method definitionl Schema and physical organization modificationl Granting user authority to access the databasel Specifying integrity constraintsl Acting as liaison with usersl Monitoring performance and responding to changes in requirements3、a) U2, U3 and U5;b)U1, U3, U4 and U5.4、 result = ADresult = ABCD(A C and A B)result = ABCDE(CD E and CD ADBC)result = ABCDEH(CD H and CD ADBCE)Is AD a candidate key? 1. Is AD a super key?1 Does AD R? = Is (AD)+ R2. Is any subset of AD a superkey?1 Does A R? = Is (A)+ R2 Does D R? = Is (D)+ R？5、The relation schema SCT is not in BCNF. After decomposition the relation schemas are: IV、 Complete the following queries. 1.a)customer_name (borrower) customer_name (depositor)b)account account s branch_name = “Perryridge” (account )c)account account (“Perryridge”, A-973, 1200)depositor depositor (“Smith”, A-973)2. create table account( account_number char(10),branch_namechar(15),balancenumeric(12,2),primary key (account_number),foreign key (branch_name) references branch,check (balance =0)3.a) select loan_numberfrom loanwhere branch_name = Perryridge and amount 1200b)(select customer_name from depositor)intersect(select customer_name from borrower)c)select branch_name, avg (balance)from accountgroup by branch_namehaving avg (balance) 1200d)select loan_numberfrom loanwhere amount is nullV、 Resolve the following questions of designing. 1、E-R diagram for the university registrars office：2、The relational database corresponding to the preceding E-R diagram：student( sid, name, program)course_offering(courseno, secno, year, semester, time, room)Instructor(iid, name, department,title)courses(courseno, title, credits,