Database Design Concepts Quiz

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Questions and Answers

What is redundancy and what problems are associated with it?

Redundancy refers to the unnecessary duplication of data in a database. Problems include increased storage costs, data inconsistency, and challenges in database management.

When is a 3rd Normal Form (3NF) relation in Boyce-Codd Normal Form (BCNF), and when is it not?

A 3NF relation is in BCNF if every determinant is a candidate key. It is not in BCNF when there are functional dependencies with non-candidate key attributes determining other attributes.

What do attributes represent in an ER model?

Attributes represent the properties or characteristics of entities in an ER model. Examples include simple (name), composite (address), single-value (age), multi-value (phone numbers), and derived (age from date of birth).

What is the relationship between a superclass and its subclass?

A superclass is a more general class that contains common attributes shared by its subclasses, which represent more specific versions of the superclass. Signup and view all the answers

What is attribute inheritance, and can you provide an example?

Attribute inheritance is the mechanism by which subclasses inherit attributes from their superclass. For example, a 'Vehicle' superclass might have attributes like 'speed' and 'fuel', which are inherited by subclasses 'Car' and 'Truck'. Signup and view all the answers

How does multiplicity represent both the cardinality and the participation constraints on a relationship type?

Multiplicity indicates the number of instances of one entity that can be associated with instances of another entity, thus representing both cardinality (like one-to-many) and participation constraints (like mandatory participation). Signup and view all the answers

What is fan in an ER model, and how can it be resolved?

Fan occurs when a single entity is related to multiple entities through different relationships. It can be resolved by restructuring the model to create a new entity that captures the shared aspect of these relationships. Signup and view all the answers

What does an ER diagram represent in the context of a library?

An ER diagram for a library represents entities such as 'Book', 'Borrower', and 'Loan', along with their attributes and the relationships between them. Signup and view all the answers

What are functional dependencies and how do they relate to the 3rd normal form (3NF)?

Functional dependencies define the relationship where one attribute uniquely determines another. They are crucial in identifying whether a table is in 3NF, as 3NF must eliminate transitive dependencies. Signup and view all the answers

What is a transitive dependency?

A transitive dependency occurs when a non-key attribute is dependent on another non-key attribute rather than directly on the primary key. Signup and view all the answers

Study Notes

Assignment 02

Due date: 27 September 2024
Unique number: 286114
Covers all chapters in the syllabus

Question 1: Database Design Concepts

Redundancy: Duplication of data within a database.
Problems associated with redundancy:
- Data inconsistency: Difficulties in maintaining data integrity when updates are required across redundant data.
- Data anomalies: Problems that arise from redundancy, like insertion, deletion, or update anomalies.
3NF and BCNF:
- 3NF: A relation in 3NF has no redundant data and is free from transitive dependencies.
- BCNF: A more restrictive form of normalization than 3NF. A relation in BCNF fulfills all requirements of 3NF and additionally, every determinant in the relation is a candidate key.
- Example: (Not using ChatGPT) Consider a table with attributes: StudentID, Name, Department, DepartmentAddress. If Department determines DepartmentAddress, the table is in 3NF. However, if StudentID is the only candidate key and is not a determinant of any attribute, the table is in BCNF.
Attributes in ER Model:
- Attributes represent properties of entities in an ER model. An attribute can be:
  - Simple: Represented by a single value (e.g. Name).
  - Composite: Composed of multiple components (e.g. Address).
  - Single-valued: Can only have one value (e.g. ID).
  - Multi-valued: Can have multiple values (e.g. Hobbies).
  - Derived: Calculated from other attributes (e.g. Age).
Superclass and Subclass:
- Superclass: A more general entity type that encompasses multiple specialized entity types.
- Subclass: A more specialized entity type that inherits attributes from the superclass. Represents a narrower category within the scope of the superclass.
Attribute Inheritance:
- Attribute inheritance: Subclasses inherit attributes from their superclasses.
- Example: Suppose you have a superclass Employee with attributes Name, ID, and Salary. A subclass Manager inherits these attributes and adds its own attribute Department.
Multiplicity in Relationships:
- Multiplicity: Describes the number of instances of one entity that can be associated with an instance of another entity in a relationship.
- Cardinality: The minimum and maximum number of instances of one entity that may be associated with one instance of another entity. (Minimum and maximum value)
- Participation: Whether an entity must participate in a relationship or not.
Fan in ER Model:
- Fan: Occurs when an entity is associated with two or more other entities through different relationships, forming a complex data structure.
- Resolution:
  - Fact Table: Create a new entity representing a fact related to the involved entities.
  - Combining entities: Merge the entities from the fan structure to form a single entity.

Question 2: Library ER Diagram

This question asks you to design an ER diagram for a library database.
Entities: Borrower, Book, Copy, BookLoan.
Relationships:
- 'borrower' 'loans' 'book' (1:M)
- 'book' 'has' 'copy' (1:M)
- 'borrower' 'loans' 'copy' (M:M)

Question 3: Normalization and Functional Dependencies

Functional Dependencies:
- Identify all functional dependencies in the Session table and convert them to 3NF.
- Use the provided table columns.
Transitive Dependency: Occurs when a non-key attribute is dependent on another non-key attribute, which is not the primary key, violating 3NF.
Example: Suppose a table has attributes City, State, and Zip Code. City determines State and State determines Zip Code. This implies a transitive dependency, violating 3NF. To correct it, create separate tables for City/State and State/Zip Code.

Question 4: SQL Queries

This question asks you to write SQL queries based on the provided data and schema.
You are to use SQL commands to address the specific questions:
- Using the Trip table, provide a sample of the data for a TripID, TripName, StartLocation and Province.
- SQL uses SELECT, FROM, WHERE statements for retrieval of data, JOIN statements for combining data from multiple tables, and GROUP BY and HAVING statements for summarizing data.

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Description

Test your knowledge of database design concepts, including redundancy, 3NF, and BCNF. This quiz covers all chapters in the syllabus and is essential for understanding data integrity and normalization principles.