Database Concepts Quiz
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Questions and Answers

Which attribute can have multiple values?

  • Composite attribute
  • Single-value attribute
  • Simple attribute
  • Multivalued attribute (correct)

A composite attribute cannot be subdivided.

False (B)

What is a derived attribute?

An attribute whose value can be calculated from other attributes.

Multivalued attributes should not be implemented in M:N relationships, and it is recommended to create new attributes for each of the original multivalued attributes' __________.

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

Match the following attribute types to their definitions:

<p>Composite attribute = Can be subdivided Simple attribute = Cannot be subdivided Single-value attribute = Can have only a single value Multivalued attribute = Can have many values</p> Signup and view all the answers

Which of the following is true about single-value attributes?

<p>They can only have one value. (C)</p> Signup and view all the answers

Derived attributes must always be stored physically in the database.

<p>False (B)</p> Signup and view all the answers

What should be done instead of implementing multivalued attributes in M:N relationships?

<p>Create several new attributes or a new entity composed of the original components.</p> Signup and view all the answers

What does an Entity Relationship Diagram (ERD) primarily represent?

<p>The conceptual database as viewed by the end user (B)</p> Signup and view all the answers

An entity in the context of ER modeling refers to a single occurrence of data.

<p>False (B)</p> Signup and view all the answers

What shape is used to represent an entity in the Chen and Crow's Foot models?

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

In an ERD, the name of an entity is written in ______ letters.

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

Which of the following components is NOT a main part of an ERD?

<p>Indexes (B)</p> Signup and view all the answers

Conflicting goals in real-world database design are rare and easily reconciled.

<p>False (B)</p> Signup and view all the answers

What term is used to describe the connections between entities in an ERD?

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

Match the following terms with their descriptions:

<p>Entities = Refers to a set of related data Attributes = Describes characteristics of an entity Relationships = Defines how entities are connected ERD = Visual representation of the database structure</p> Signup and view all the answers

What type of relationship exists between occurrences of the same entity set?

<p>Unary relationship (D)</p> Signup and view all the answers

Associative entities are also known as bridge entities.

<p>True (A)</p> Signup and view all the answers

What is the primary purpose of associative entities?

<p>To implement M:N relationships.</p> Signup and view all the answers

An associative entity is composed of the primary keys of __________ entities to be connected.

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

What can an associative entity contain besides primary keys?

<p>Additional attributes (B)</p> Signup and view all the answers

Unary relationships can occur only between two different entity sets.

<p>False (B)</p> Signup and view all the answers

What is another term for an associative entity?

<p>Bridge entity</p> Signup and view all the answers

What type of relationship requires that one entity occurrence must correspond to a specific entity occurrence?

<p>Mandatory participation (A)</p> Signup and view all the answers

A unary relationship involves three entities.

<p>False (B)</p> Signup and view all the answers

What does the degree of a relationship indicate?

<p>The number of entities or participants associated with a relationship.</p> Signup and view all the answers

In a ______ relationship, two entities are associated.

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

Match the type of relationship with its definition:

<p>Unary relationship = Association maintained within a single entity Binary relationship = Association between two entities Ternary relationship = Association involving three entities Optional participation = Entity occurrence does not require a corresponding entity occurrence</p> Signup and view all the answers

Which of the following statements is TRUE regarding optional participation?

<p>It does not require a corresponding entity occurrence. (B)</p> Signup and view all the answers

A ternary relationship involves two associated entities.

<p>False (B)</p> Signup and view all the answers

What type of relationship does not require a corresponding entity occurrence?

<p>Optional participation</p> Signup and view all the answers

What type of relationship exists if the primary key of the related entity does not contain a primary key component of the parent entity?

<p>Weak relationship (A), Non-identifying relationship (B)</p> Signup and view all the answers

A weak entity has its primary key totally independent of the parent entity.

<p>False (B)</p> Signup and view all the answers

What two conditions must a weak entity meet?

<p>Existence-dependent and primary key partially or totally derived from parent entity</p> Signup and view all the answers

A strong relationship exists when the PK of the related entity contains the ___ component of the parent entity.

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

Which of the following best describes a weak entity?

<p>Dependent on the existence of a parent entity (A), Has a primary key wholly derived from a parent entity (B)</p> Signup and view all the answers

The classification of an entity as weak is solely determined by its primary key.

<p>False (B)</p> Signup and view all the answers

The classification of a weak entity is influenced by ___ rules.

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

What is NOT a typical conflicting goal for database designers?

<p>User satisfaction (A)</p> Signup and view all the answers

An entity relationship model (ERM) must always represent the actual database structure exactly as implemented.

<p>False (B)</p> Signup and view all the answers

Name the main components of an entity relationship model (ERM).

<p>Entities, Relationships, Attributes</p> Signup and view all the answers

A M:N relationship must be mapped to a set of ______ relationships.

<p>1:M</p> Signup and view all the answers

Match the following terms with their correct descriptions:

<p>Entity = A real-world object or concept represented in a database Relationship = The association between entities Attribute = A characteristic of an entity Cardinality = The number of instances of one entity related to another entity</p> Signup and view all the answers

Which of the following is a key factor database designers must consider when designing databases?

<p>Logical requirements (D)</p> Signup and view all the answers

Connectivity in an ERD only refers to the number of entities involved.

<p>False (B)</p> Signup and view all the answers

What diagram is used to represent the static data structures in a data model?

<p>UML class diagram</p> Signup and view all the answers

Flashcards

Entity Relationship Model (ERM)

A model that forms the basis for an Entity Relationship Diagram (ERD). It represents a conceptual database as seen by end users.

Entity Relationship Diagram (ERD)

A visual representation of a database's main components (entities, attributes, and relationships).

Entities

Represent groups of things (like product or customer). In an ERD, they're depicted using rectangles.

Attributes

Properties of entities (like product name, price).

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Relationships

Connections between entities. These are crucial for database functionality.

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Entity Set

A collection of similar entities, not a specific instance of an entity.

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Entity Occurrence

A single instance of something that belongs to an entity set.

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ERD Components

Entities, attributes, and relationships together form database foundation.

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Composite Attribute

An attribute that can be further broken down into smaller attributes.

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Simple Attribute

An attribute that cannot be divided into smaller attributes.

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Single-Value Attribute

An attribute that can only have one value.

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Multivalued Attribute

An attribute that can have multiple values.

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M:N Relationship

A relationship that involves two entities in which one entity can relate to multiple entities of the other, and vice versa.

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Multivalued attribute implementation

A database design strategy that is a bad approach when dealing with Multivalued Attributes.

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Derived Attribute

An attribute whose value is calculated from other attributes.

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Attribute Handling (M:N)

To avoid issues with implementing M:N relationships, create new attributes and possibly a new entity for multiple values within a single attribute.

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Weak Relationships

A relationship where the primary key of the related entity does not contain the primary key component of the parent entity.

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Strong Relationships

A relationship where the primary key of the related entity contains the primary key component of the parent entity.

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Weak Entity

An entity that meets two conditions: existence-dependent and its primary key is partially or totally derived from the parent entity in the relationship.

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Existence-dependent

A weak entity cannot exist without a related strong entity.

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Primary Key

A unique identifier for each record in a table.

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Parent Entity

The entity from which the weak entity depends.

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Business Rules

The rules that determine whether an entity is weak or strong.

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Relationship Strength

Weak and Strong relationships, determining the level of dependencies.

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Optional Participation

One entity occurrence does not need a corresponding entity occurrence in a specific relationship.

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Mandatory Participation

One entity occurrence needs a corresponding entity occurrence in a specific relationship.

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Unary Relationship

An association maintained within a single entity.

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Binary Relationship

A relationship between two entities.

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Ternary Relationship

A relationship among three entities.

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Relationship Degree

Indicates the number of entities involved in a relationship.

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Relationship Participation

Describes whether an entity occurrence is required in a relationship.

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Entity Participation

Describes if an entity occurrence needs a corresponding entity in a specific relationship.

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Recursive Relationship

A relationship between occurrences of the same entity set. This kind of relationship is seen in unary relationships.

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Associative Entity

An entity used to represent a many-to-many relationship between two other entities. It acts as a bridge and includes primary keys from both entities.

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Bridge Entity

Another term for an associative entity, highlighting its role in connecting entities.

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What is the purpose of an associative entity?

Associative entities are used to implement many-to-many relationships between entities. They serve as a bridge, combining information from both related entities.

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Why use a bridge entity?

A bridge entity, or associative entity, is used to represent complex relationships between entities. It allows us to manage many-to-many relationships, preventing data redundancy and improving data integrity.

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Can associative entities have additional attributes?

Yes, associative entities can have additional attributes that are not directly involved in the connecting process. These attributes can provide further details about the relationship.

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Conflicting Goals in DB Design

Database design often involves balancing competing needs, such as performance, data integrity, and user requirements.

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Design Standards in DB

These are guidelines dictating how a database should be structured and implemented, ensuring consistency and ease of maintenance.

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Processing Speed vs. Data Needs

Balancing the need for fast data retrieval with the comprehensive data requirements of users can be a challenge in database design.

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Logical Requirements in DB Design

These describe how the database should function and what data it needs to store. They are vital for ensuring the database meets user expectations.

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M:N Relationship (ER Model)

Represents a many-to-many connection between entities, meaning one entity can have multiple links to another. This is common in real-world scenarios.

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Mapping M:N to 1:M

Transforming a many-to-many relationship in the ER model into a set of one-to-many relationships, which is required for efficient database implementation.

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UML Class Diagrams

Used to represent the static data structures of a data model in a visual way, helping developers understand the database structure and organization.

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Design Compromises in DB

Database design often requires making trade-offs between different goals, resulting in decisions that might not be ideal but achieve the most important requirements.

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Study Notes

Database Principles: Fundamentals of Design, Implementation, and Management, Tenth Edition

  • Chapter 7 covers Data Modeling with Entity Relationship Diagrams
  • Objectives:
    • Students will learn the main characteristics of entity relationship components
    • Students will learn how relationships between entities are defined, refined, and incorporated into the database design process.
    • Students will learn how ERD components affect database design and implementation
    • Students will learn that real-world database design often requires the reconciliation of conflicting goals
  • The Entity Relationship Model (ERM) forms the basis of an ER diagram
  • ERD represents the conceptual database from the end user's perspective.
  • ERDs depict the database's main components--Entities, Attributes, Relationships
  • Entities refer to entity sets, not single entities. Each entity corresponds to a table, not a row.
  • In Chen and Crow's Foot models, entities are represented as rectangles containing the entity's name.
  • Entity names are nouns written in capital letters.
  • Attributes are characteristics of entities.
  • Chen notation: attributes are represented by ovals connected to the entity rectangle by a line. Each oval contains the attribute's name.
  • Crow's foot notation: Attributes are written inside boxes below the entity rectangle
  • Required attribute: must have a value
  • Optional attribute: may be left empty
  • Domain: set of possible values for an attribute
  • Attributes may share a domain
  • Identifiers: one or more attributes that define each entity instance uniquely
  • Composite identifier: primary key composed of more than one attribute
  • Composite attribute - can be subdivided
  • Simple attribute - cannot be subdivided
  • Single-value attribute - can have only one value
  • Multivalued attribute - can have many values
  • M:N relationships and multivalued attributes should not be implemented
  • Create several new attributes for each of the original multivalued attributes' components
  • Create a new entity composed of original multivalued attributes' components
  • Derived attribute: calculated from other attributes. Not necessarily stored in the database.
  • Relationships represent associations between entities
  • Relationships always operate in both directions.
  • Relationships can be classified as 1:M
  • Relationship classification can be difficult to establish if only one side of the relationship is known
  • Connectivity - describes the relationship classification
  • Cardinality - expresses the minimum and maximum number of entity occurrences associated with one occurrence of a related entity
  • Existence dependence: An entity exists in the database only when associated with another related entity's occurrence.
  • Existence independence: An entity can exist apart from one or more related entities. Sometimes a strong entity.
  • Weak (non-identifying) relationships exist if the primary key of a related entity does not contain the primary key component of the parent entity
  • Strong (identifying) relationships exist if the primary key of a related entity contains the primary key component of the parent entity
  • Optional participation means one entity occurrence does not require a corresponding entity occurrence in a particular relationship
  • Mandatory participation means one entity occurrence requires a corresponding entity occurrence in a particular relationship
  • Relationship degree: Indicates the number of entities involved in a relationship.
    • Unary: association within a single entity
    • Binary: association between two entities
    • Ternary: association between three entities
  • Recursive relationships exist when a relationship can exist between occurrences of the same entity set. This frequently occurs in a unary relationship.
  • Associative (composite) entities, also known as bridge entities, are used to implement M:N relationships. Composed of primary keys of each of the entities to be connected. May also contain additional attributes that play no role in the connective process.
  • Converting M:N relationships into two 1:M relationships involves use of a composite (association) entity to handle the relationship.
  • Designing an ER diagram is an iterative process. Steps include:
    • Creating a detailed narrative
    • Identifying business rules
    • Identifying main entities and relationships
    • Making a first ERD
    • Identifying attributes and primary keys
    • Revise and review ERD

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Database Principles: Fundamentals of Design, Implementation, and Management PDF

Description

Test your knowledge on database attributes, including composite, derived, and multivalued attributes. This quiz will challenge your understanding of Entity Relationship Diagrams (ERDs) and the best practices in database design. Perfect for learners of database management systems.

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