Unit 2: E-R Modeling - Practice Quiz

1 What does ER modeling primarily represent?

2 What is the main purpose of an ER diagram?

3 What is an entity in an ER model?

4 Which of the following is an example of an entity?

5 What is an attribute?

6 Which attribute can be divided into smaller components?

7 What does a relationship describe in an ER model?

8 Which shape commonly represents an entity in an ER diagram?

9 Which shape commonly represents an attribute in an ER diagram?

10 Which shape commonly represents a relationship in Chen notation?

11 What does a double oval usually represent?

12 During ER-to-relational conversion, an entity is usually mapped to what?

13 How is a one-to-many relationship commonly represented in relational schemas?

14 What is commonly created for a many-to-many relationship?

15 What does the letter A in ACID stand for?

16 Which ACID property ensures that committed data is not lost after a system failure?

17 What does isolation ensure in database transactions?

18 Which constraint prevents a column from containing NULL values?

19 Which constraint requires values in a column to be different?

20 What is a primary key used for?

21 A university system stores information about students, courses, and enrollments. Which ER modeling approach best represents the fact that one student can enroll in many courses and one course can have many students?

22 In a hospital database, a patient has multiple phone numbers, and each phone number may be shared by members of the same household. How should phone number be modeled?

23 In standard Chen notation, which symbol represents a relationship set in an ER diagram?

24 An ER model contains an entity Employee with key EmployeeID and a multivalued attribute Skill. Which relational mapping is appropriate?

25 A transaction transfers money from Account A to Account B. Which ACID property ensures that both the debit and credit occur together or neither occurs?

26 A relation Student(StudentID, Name, DepartmentID) contains a foreign key DepartmentID referencing Department(DepartmentID). Which operation may violate referential integrity?

27 A relation Employee has attributes EmployeeID, Email, Name, and Department. Both EmployeeID and Email uniquely identify every employee, and EmployeeID is selected as the primary key. What is Email?

28 A company wants to record the date on which each employee joins a project. Where should JoinDate be modeled when an employee can work on many projects and a project can have many employees?

29 A dependent cannot be uniquely identified without the Employee who supports the dependent. Which ER concept best represents Dependent?

30 In an ER diagram, a double line connects the entity Employee to the relationship AssignedTo. What does this notation usually indicate?

31 For a one-to-many relationship between Department and Employee, where one department has many employees, where is the foreign key normally placed?

32 A transaction commits successfully, but the database server loses power immediately afterward. Which mechanism primarily supports recovery of the committed changes?

33 Which constraint prevents two rows in a relation from having the same value for a declared primary key?

34 A relation OrderLine(OrderID, ProductID, Quantity) uses the combination of OrderID and ProductID to identify each row. What type of key is this combination?

35 A library records books and their authors. A book may have several authors, and an author may write several books. Which modeling decision is most appropriate?

36 A customer address is stored as Street, City, State, and PostalCode, and users sometimes need the complete address and sometimes only the city. What type of attribute is Address?

37 An ER diagram contains a relationship connecting the Employee entity to itself to represent supervision. What type of relationship is this?

38 A ternary relationship Supplies connects Supplier, Part, and Project. Which mapping preserves each specific supplier-part-project association?

39 Two concurrent transactions update the same inventory item. Which ACID property prevents one transaction from observing an inconsistent intermediate update by the other?

40 A column Age is defined to accept integer values from 18 through 65. Which constraint enforces this requirement?

41 A university system stores students, courses, and enrollments. A student may enroll in many courses, and a course may have many students. Each enrollment has a grade and a registration timestamp. What is the most semantically accurate ER modeling choice?

42 A person can have several phone numbers, each phone number can belong to multiple people, and the same number may be labeled differently for each person. Which model best captures this requirement?

43 In an ER diagram, every dependent must be associated with exactly one employee, while an employee may have zero or many dependents. Which cardinality and participation combination is correct?

44 An identifying relationship connects strong entity Employee to weak entity Dependent. Dependent has partial key DependentName, and its owner key is EmployeeID. Which relational design is correct?

45 A transaction transfers money by debiting one account and crediting another. The system must ensure that a crash cannot leave only one update committed. Which ACID property and implementation mechanism are most directly involved?

46 A relation Employee(EmployeeID, ManagerID) represents a management hierarchy. Every non-null ManagerID must reference an existing EmployeeID, but the top-level employee has no manager. Which constraint combination is required?

47 For relation Registration(StudentID, CourseID, Semester, Grade), assume a student can register for a course once per semester. Which statement correctly identifies a candidate key?

48 A hospital treats recurring episodes for patients. Each treatment episode has its own diagnosis and admission date, while a patient may have many episodes. Which modeling choice avoids incorrectly attaching episode-specific data to the patient?

49 A customer address consists of street, city, state, and postal code, but customers may have multiple addresses, each classified as billing or shipping. Which decomposition is most appropriate?

50 A relationship has cardinality 1:N from Department to Employee, and every employee must belong to exactly one department. In standard ER notation, which interpretation is correct?

51 An M:N relationship WorksOn between Employee and Project has attributes Hours and AssignmentDate. Which mapping is correct?

52 Transaction T1 reads a balance, transaction T2 updates and commits that balance, and T1 later reads it again during the same transaction. Which isolation phenomenon occurs if the two values differ?

53 A database requires every order item to reference an existing order, prohibits negative quantities, and prevents duplicate products within one order. Which constraint set enforces all three rules?

54 Relation Flight(FlightNo, FlightDate, Origin, Destination) permits the same flight number on different dates. Which key choice is most appropriate if a flight instance is uniquely identified by its number and date?

55 A 1:1 relationship between Person and Passport is mandatory for Passport but optional for Person. Passport is best stored with a foreign key to Person. Where should the relationship's attribute IssueDate be stored?

56 After a transaction commits, the database server loses power before dirty pages reach disk. Which mechanism primarily ensures the committed changes can be recovered?

57 A company employs people who may serve as engineers, managers, or both. Every employee must belong to at least one of these categories, and category-specific attributes differ. Which specialization constraint is appropriate?

58 A project has multiple phases, and phase numbers are unique only within a project. A phase cannot exist independently of its project. How should Phase be modeled?

59 In a ternary relationship Supplies(Supplier, Part, Project), the constraint says that for a given Supplier and Project, at most one Part is supplied. Which key constraint does this imply?

60 A table stores nullable values in a column covered by a UNIQUE constraint. Under standard SQL semantics, which statement is generally correct?