UNIVERSITY OF TORONTO MIDTERM TEST SUMMER 2017 CSC343H Introduction to Databases Instructor Tamanna Chhabra Duration 120 min No aids allowed

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1 UNIVERSITY OF TORONTO MIDTERM TEST SUMMER 2017 CSC343H Introduction to Databases Instructor Tamanna Chhabra Duration 120 min No aids allowed This test is worth 15% of your final mark. Please answer all questions in the space provided. You may use the blank pages dispersed throughout the exam for rough work. In your answers try to be concise. Good luck! Last Name First Name Student Number Marks Q1 Q2 Q3 Q4 Q5 Q6 Total Page 1 of 13

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3 1. [4 Marks] Given two relations R1 and R2 (union-compatible), where R1 contains N1 tuples and R2 contains N2 tuples, and N2 > N1 > 0, give the maximum and minimum possible sizes (in tuples) for the resulting relation produced by each of the following relational algebra expressions. (a) R1 R2 Minimum- N2 Maximum N1+N2 (b) R1 R2 Minimum- 0 Maximum-N1 (c) R1 - R2 Minimum- 0 Maximum-N1 Page 3 of 13

4 (d) R1 R2 Minimum- N1*N2 Maximum-N1*N2 2. Which of the following pairs of relational algebra expressions give the same answer, i.e. are what we would call equivalent? Assume the relations being used are R(A, B, C, D) and S(C, D, E). a. [1 Mark] R S AND σ R.C=S.C (R S) Not equivalent b. [1 Mark] σ A=5 and D= any (R S) AND σ A=5 (R) σ D= any (S) Equivalent Page 4 of 13

5 c. [1 Mark] π C,D ( σ A=5 (R)) π C,D (S) AND σ A=5 (π C,D (R) π C,D (S)) Not equivalent 3. Write True/ for each of the following: a. [1 Mark] Given 2 union-compatible tables M and N with 100 rows and 20 rows respectively. The minimum number of rows in (M (M N)) is 20. b. [1 Mark] Given: The primary key of a table is made up columns x and y. In a given row, either x or y can be null, but not both. Page 5 of 13

6 c. [1 Mark] Given 2 tables: sailor1(sid, sname, rating) and sailor2(s#, name, True rating). These 2 tables are union-compatible. d. [1 Mark] The columns of a relation are sometimes called "tuples." e. [1 Mark] A relation can have only one candidate key. f. [1 Mark] A weak entity is an entity that cannot exist in the database without (and is logically dependent upon) another type of entity also existing in the database. True g. [1 Mark] In the relational model, cardinality is referred to as the number of attributes in a relation. Page 6 of 13

7 h. [1 Mark] In case of entity integrity, primary key can be null. i. [1 Mark] Relational Algebra is procedural query language. True j. [1 Mark] The Union operation ( ) can be performed between any two relations. 4. Consider the database schema below and answer the queries that follow. Employee(Ssn, Bdate, Fname, Minit, Lname, address, salary, Sex, SuperSsn, Dno) Department(Dnum, Name, Mgr_Ssn, Mgr_Start_date) Dept_location(Dnumber, Dlocation ) Project(Pnumber, Pname, Plocation, Dnum) Works_On(Essn, Pno, Hours) Depenedant(Essn, Dependantname, Sex, Bdate, Relationship) Employee(SuperSsn) Employee(Ssn) Employee(Dno) Department(Dnum) Department(Mgr_Ssn) Employee(Ssn) Dept_location(Dnumber) Department(Dnum) Page 7 of 13

8 Project(Dnum) Department(Dnum) Works_On(Essn) Employee(Ssn) Works_On(Pno) Project(Pnumber) Dependant(Essn) Employee(Ssn) a. [1 Mark] Retrieve the first names of all employees in department 5 who work more than 10 hours per week on the ProductX project. b. [1 Mark] List the first names of all employees who have a dependent with the same first name as themselves. Page 8 of 13

9 c. [1 Mark] Find the first names of all employees who are directly supervised by FranklinWong. d. [1 Mark] Retrieve the first names of all employees who do not work on any project. Page 9 of 13

10 e. [1 Mark] List the last names of all department managers who have no dependents. 5. [4 Marks] Create an ER diagram for the following description: a. Each company (CompanyID, Company Name) operates multiple departments (DepartID and Dept Name) and each department must belong to a company. b. Each department employs zero or more employees (Employee ID, Employee Name) but each employee must work for a department. c. Each of the employees may or may not have dependants (Dependant Name), but each dependant must belong to one employee. Page 10 of 13

11 d. Each employee may or may not have an employment history (History ID, details) but each employment history belongs to one employee. Company ID DeptID DeptName Company Oper ates Departments Company Name EmployeeID employs o Dependant Has Employee EmployeeName Dependant_Name Have HistoryID Employment History Page 11 of 13 details

12 6. [4 Marks]Convert the following ER Model into Relational Model. Manufacturer(name, city, street) Part(part-num,description,mname) Order(order-num,CID) Customer(ID, name) Contains(order-num, CID, part-num, quantity) Part(mname) Maufacturer(name) Contains(order-num) Order(order-num) Page 12 of 13

13 Contains(CID) Customer(ID) Contains(part-num) Part(part-num) Order(CID) Customer(ID) Page 13 of 13