数据库课堂测验.docx

终极预测【基于课堂作业】********************************【考试题预测】******************************1、给相应的文字描述写出先关的操作！（第2章）【必考】【给个例题】Consider the relational database of Figure 2.35, where the primary keys are un-derlined. Give an expression in the relational algebra to express each of the fol-lowing queries:a. Find the names of all employees who work for First Bank Corporation.b. Find the names and cities of residence of all employees who work for FirstBank Corporation.c. Find the names, street address, and cities of residence of all employees whowork for First Bank Corporation and earn more than $10,000 per annum.d. Find the names of all employees in this database who live in the same cityas the company for which they work.e. Assume the companies may be located in several cities. Find all companieslocated in every city in which Small Bank Corporation is located.employee (person-name, street, city)works (person-name, company-name, salary)company (company-name, city)manages (person-name, manager-name)Figure 2.35. Relational database for Exercises 2.1, 2.3 and 2.9.Answer:a. Πperson-name (σcompany-name =“First Bank Corporation” (works)) 【例题2】2.7 Consider the relational database of Figure 2.35. Give an expression in the rela-tional algebra for each request:a. Give all employees of First Bank Corporation a 10 percent salary raise.b. Give allmanagers in this database a 10 percent salary raise, unless the salarywould be greater than $100,000. In such cases, give only a 3 percent raise.c. Delete all tuples in the works relation for employees of Small Bank Corpora-tion.2、SQL查询语言的考察（第3、4章）【╮(╯▽╰)╭还是必考内容，而且考点多很分散】【参见作业！！以下是作业的精选题！！】3、将描述的关系和实体用ER图表示出来并绘制ER图（第6章）【这个我想地球人都知道】【给个例子吧！】绘制 E-R 图，要求在图中表示联系的类型，最后转换成关系表，并指明主键。 实体 1：学生，属性：学号、姓名、性别、年龄。主标识符：学号 实体 2：课程，属性：课程号、课程名、学分数。主标识符：课程号 注：一个学生可以选多门课程，一门课程也可以被多个学生选，学生选课后有成绩。 4、函数的推导以及闭包运算（第7章）【例子如下！】To prove that :if α → β and α → γ then α → βγFollowing the hint, we derive:α → β givenαα → αβ augmentation ruleα → αβ union of identical setsα → γ givenαβ