Database Management Systems Quiz
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Questions and Answers

What describes the structure and constraints for the whole database for a community of users?

  • Internal schema
  • Data dictionary
  • External schema
  • Conceptual schema (correct)

    • Which option provides database query and transaction services to the clients?

  • Database Server (correct)
  • File Server
  • Schema Server
  • Data Warehouse

    • Specific items or objects in the mini-world that are represented in the database are referred to as what?

  • Schemas
  • Attributes
  • Classes
  • Entities (correct)

    • Which of the following correctly identifies the types of attributes?

    <p>Composite</p> Signup and view all the answers

    What type of relationship does a cardinality ratio of one-to-one indicate?

    <p>Each entity in one set is associated with one entity in another set</p> Signup and view all the answers

    Changes in what will occur every time the database is updated?

    <p>Database instance</p> Signup and view all the answers

    Which term specifies maximum participation in a relationship?

    <p>Participation constraint</p> Signup and view all the answers

    What is true regarding entity types and keys?

    <p>An entity type can have more than one key.</p> Signup and view all the answers

    What is one of the main responsibilities of a Database Administrator (DBA)?

    <p>Creating users and authorizing access to the database</p> Signup and view all the answers

    Which of the following is NOT a characteristic of the database approach?

    <p>Static data structure</p> Signup and view all the answers

    What could be a consequence of data redundancy?

    <p>Data inconsistency</p> Signup and view all the answers

    Which DBMS function involves generating reports or processing user queries?

    <p>Data retrieval</p> Signup and view all the answers

    What is a primary function of a database backup service?

    <p>Create backup files to restore data if needed</p> Signup and view all the answers

    Which of the following is a task of database designers?

    <p>Defining content and structure of the database</p> Signup and view all the answers

    What problem can arise from having multiple views in a database?

    <p>Data inconsistency issues</p> Signup and view all the answers

    Which statement correctly describes the purpose of processing and sharing by a DBMS?

    <p>To maintain data validity and consistency among concurrent users</p> Signup and view all the answers

    What is a Unary Relationship?

    <p>A relationship between entities of the same type.</p> Signup and view all the answers

    What type of keys can a database key be classified as?

    <p>Simple or composite keys.</p> Signup and view all the answers

    Which statement is true regarding weak entity sets?

    <p>They do not have a primary key.</p> Signup and view all the answers

    In the COMPANY database scenario, what attribute is NOT associated with an employee?

    <p>Academic qualifications</p> Signup and view all the answers

    Which of the following best describes a department in the COMPANY database?

    <p>It is managed by an employee and may have multiple locations.</p> Signup and view all the answers

    What defines the participation between employee and project?

    <p>Employees may work on multiple projects but are linked to a single department.</p> Signup and view all the answers

    What is an example of an attribute related to dependents in the COMPANY database?

    <p>Dependent's relationship</p> Signup and view all the answers

    What role do database users typically play?

    <p>They both use and design the database software.</p> Signup and view all the answers

    What is the primary action in specialization within an EER model?

    <p>Defining subclasses of an entity type</p> Signup and view all the answers

    In generalization, what is typically done with multiple entity types?

    <p>They are combined based on shared properties</p> Signup and view all the answers

    Which of the following statements is true regarding attribute inheritance in subclasses?

    <p>Subclasses inherit all attributes from their superclass</p> Signup and view all the answers

    What does the disjointness constraint ensure in specialization?

    <p>Entities belong exclusively to one subclass</p> Signup and view all the answers

    What is the main difference between total completeness and partial completeness in constraints?

    <p>Total completeness requires entities to belong to at least one subclass, while partial allows some to be unmatched</p> Signup and view all the answers

    What is the role of a primary key in a table?

    <p>To uniquely identify each row and prevent duplicate data</p> Signup and view all the answers

    Which of the following best describes the overlapping constraint?

    <p>Allows entities to belong to more than one subclass</p> Signup and view all the answers

    Which example correctly illustrates the specialization and disjointness constraint?

    <p>An employee specializing strictly as SECRETARY</p> Signup and view all the answers

    Which statement about candidate keys is true?

    <p>There can be multiple candidate keys per table</p> Signup and view all the answers

    What is implied by a super key?

    <p>It may include other non-unique attributes</p> Signup and view all the answers

    How do subclasses interact with relationships inherited from their superclasses?

    <p>Subclasses inherit all relationships from superclasses</p> Signup and view all the answers

    Which of the following is true regarding the use of NULL values in a relation?

    <p>NULL values represent unknown or not applicable data</p> Signup and view all the answers

    Which type of constraint ensures that no duplicate rows exist in a relation?

    <p>Entity integrity constraints</p> Signup and view all the answers

    What does the term 'secondary key' refer to?

    <p>Any candidate key not chosen as the primary key</p> Signup and view all the answers

    Which of the following statements about constraints is false?

    <p>Key constraints are the only type of constraints used</p> Signup and view all the answers

    How many primary keys can there be per table?

    <p>One</p> Signup and view all the answers

    What does completeness constraint specify about entities in a superclass?

    <p>Entities can exist without belonging to any subclass.</p> Signup and view all the answers

    Which type of specialization requires that every entity in the superclass must belong to one and only one subclass?

    <p>Disjoint specialization with exclusive membership.</p> Signup and view all the answers

    What is the significance of a key in a relation?

    <p>It uniquely identifies each row in the relation.</p> Signup and view all the answers

    What aspects are included in the domain of a relation?

    <p>Data type, size, logical meaning, and role.</p> Signup and view all the answers

    In the context of relational databases, what are rows typically referred to as?

    <p>Tuples</p> Signup and view all the answers

    Which type of subclasses allows entities in the superclass to belong to multiple subclasses?

    <p>Overlapping subclasses with optional membership.</p> Signup and view all the answers

    What does an attribute name refer to in a formal model?

    <p>A column header in a table.</p> Signup and view all the answers

    What is meant by specializing subclasses that are disjoint?

    <p>No entity from the superclass shares a subclass.</p> Signup and view all the answers

    Study Notes

    Q1 - Choose the Correct Answer

    • A database is an organized, structured set of data about a specific subject.
    • A database management system (DBMS) is software that enables users to create and maintain databases.
    • DBMS software manages the database, including database manipulation, maintenance, and data recovery.
    • Database administrators (DBAs) are responsible for tasks such as creating users, controlling database use, and ensuring efficient database operations.
    • Database models define the structure of a database, including data types and constraints.
    • Problems with data redundancy include wasted storage space and increased effort.
    • A database schema describes the structure of a database, operations for manipulation of these structures, and constraints.
    • A database schema includes details about database structure, data types, and required constraints.
    • Database state is the actual data stored in a database at a particular moment.

    Q2 - Select T/F

    • A valid state in a database represents the initial state when loaded. (FALSE)
    • Data duplication can cause inconsistencies. (TRUE)
    • Unique student names can be a key in a university database. (TRUE)
    • An entity type can have more than one key. (TRUE)
    • Entities are the data points that are important to a database (FALSE).
    • Conceptual database models describe data storage format. (FALSE)
    • A unary relationship is a connection between two different entities (FALSE).
    • A primary key is a unique identifier within a table (TRUE).
    • The entity set that has a primary key is a weak entity set (FALSE).

    Q3 - Database Schema Design

    • The company is structured into departments, each with a manager, number, and start date.
    • Each department may have multiple locations. Departments manage multiple projects, each with a unique name and number, and a specific location.
    • Each employee has a social security number, address, salary, sex, birthdate, a department, and works on multiple projects.
    • The employee has a supervisor and dependents with birthdate, sex, relationship to the employee
    • An entity-relationship diagram (ERD) should be created showing attributes, relationships, cardinality, and participation of all entities to meet the criteria.

    Q1. Database, DBMS, Database Systems

    • A database is an organized collection of data in a structured format, used to manage and retrieve information.
    • A DBMS is software that manages and manipulates the data within a database.
    • A database system is a combination of the database itself and the DBMS managing it, with applications sometimes involved as well.

    Q3. DBMS Facilites

    • Defining database structures, data types, and constraints.
    • Loading initial database contents onto storage devices.
    • Manipulating database content (including retrieving and modifying data)
    • Managing database deletions and updates.
    • Sharing data amongst concurrent users and application programs.

    Data Model Concepts - Attribute Types

    • Simple attributes: Hold a single value (e.g., age, name)
    • Composite attributes: Made up of multiple simple attributes (e.g., address composed of street, city, state, zip code).
    • Multi-valued attributes: Hold multiple values for a single entity (e.g., skills or phone numbers).

    Data Model Concepts - Relationships

    • Studying relationships reveals how different entities/attributes interact within a system
    • Entities interact, either directly or indirectly, throughout a system.
    • Relational models analyze connections between components for understanding.

    Data Model Concepts - Relationship Types

    • Unary relationships link an entity to itself.
    • Binary relationships connect two different entity types (e.g., employee manages department).
    • Ternary relationships connect three entity types.
    • N-ary relationships link more than three entity types.

    Data Model Concepts - Constraints on Relationships

    • Cardinality ratios specify the maximum number of relationships for an entity.
    • One-to-one (1:1): An entity in one entity type is related to exactly one entity in another.
    • One-to-many (1:N) or many-to-one (N:1): An entity in one entity type can be related to multiple entities in another (or vice versa).
    • Many-to-many (M:N): multiple entities in one entity type are related to multiple entities in another.

    Data Model Concepts - Keys

    • Entities can be uniquely identified using attributes called primary keys.
    • Attributes, that are involved in uniquely identifying an entity, are called candidate keys. The key selected to uniquely identify an entity is referred to as a primary key.
    • Primary keys play a vital role in managing relations between entities and ensuring data integrity and consistency.
    • A relation may consist of only one key. (FALSE)
    • There could be more than one key in a relation.
    • The order in which tuples (rows) appear in a table is not important. (TRUE)
    • The order in which attributes appear in a table is not important. (FALSE)

    Data Model Concepts - Data Retrieval and Constraints

    • SQL queries are used to retrieve data effectively.
    • Constraints enforce data integrity within relations (e.g., ensuring primary keys are unique).
    • Examples of constraints include defining domain values, attributes, and ensuring tables stay consistent.
    • Key constraints, entity integrity constraints, referential integrity constraints, and domain constraints are all examples of constraints.
    • A primary key is required to identify each row within a relational table.

    Data Model Concepts - Primary Keys

    • Primary keys are specific attributes in a relation for unique row identification
    • Primary keys are used to establish connections and reference entities.
    • Primary keys can have multiple attributes.

    Specialization and Generalization

    • Specialization defines a set of subclasses from a superclass, based on unique characteristics
    • Generalization reverses specialization, creating a generalized class from related subclasses.
    • Specialization and generalization are often used together in a database design, offering a top-down/bottom-up approach to representing the entities within a system.

    Attribute Inheritance

    • Subclasses inherit attributes from their superclass.
    • Subclasses also inherit relationships associated with the superclass.

    Constraints on Specialization and Generalization

    • Disjointness constraint: Entities can only belong to one subclass.
    • Overlapping constraint: Entities can belong to multiple subclasses.
    • Completeness constraint—total (at least one subclass each entry must belong to) or partial (some entries don’t have to belong to any subclass).

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    Description

    Test your knowledge on the principles of database management systems. This quiz covers essential concepts such as database structure, management, and the role of database administrators. Perfect for students learning about databases and data organization.

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