Database Modeling: Objects and Attributes Quiz
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Database Modeling: Objects and Attributes Quiz

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Questions and Answers

What is a characteristic of a strong entity?

Has its own unique identifier

How is a weak entity different from a strong entity?

Dependent on a strong entity

What does a double underline in an entity box signify?

Partial identifier

In the context of identifying relationships, what do they link together?

<p>Strong entities to weak entities</p> Signup and view all the answers

When should a relationship with attributes become an associative entity?

<p>When it links two strong entities together</p> Signup and view all the answers

What is an entity in the context of a database?

<p>An object that will be composed of multiple attributes</p> Signup and view all the answers

Which of the following is a characteristic of identifiers (keys) in a database?

<p>Will uniquely identify individual instances of an entity type</p> Signup and view all the answers

What does a composite attribute refer to in a database?

<p>An attribute broken into component parts</p> Signup and view all the answers

In the context of attributes, what does 'single-valued' imply?

<p>An attribute has a single, unique value for each entity</p> Signup and view all the answers

What is the purpose of an identifier (key) in a database?

<p>To uniquely identify individual instances of an entity type</p> Signup and view all the answers

How are identifiers (keys) differentiated from other attributes in a database?

<p>They uniquely identify individual instances of an entity type</p> Signup and view all the answers

What describes features pertaining to the association between entities in a relationship?

<p>Relationship types</p> Signup and view all the answers

In the E-R model, what is the degree of a relationship?

<p>The number of entity types participating in the relationship</p> Signup and view all the answers

What type of relationship involves three different entity types related to each other?

<p>Ternary Relationship</p> Signup and view all the answers

What does 'One-to-Many' cardinality mean in a relationship?

<p>An entity can have many related entities on one side</p> Signup and view all the answers

What defines the minimum number of instances one entity can be associated with another in an E-R diagram?

<p>Cardinality Constraints</p> Signup and view all the answers

In an E-R model, what is an instance between specific entity instances?

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

Which type of constraint specifies the maximum number of instances one entity can be associated with another in a relationship?

<p>Cardinality Constraints</p> Signup and view all the answers

What does a Unary Relationship involve in the E-R model?

<p>One entity related to another of the same entity type</p> Signup and view all the answers

What is represented by Multiple Relationships in an E-R diagram?

<p>Entities related to each other in more than one way</p> Signup and view all the answers

How is 'Many-to-Many' cardinality defined in a relationship?

<p>An entity can have many related entities on both sides</p> Signup and view all the answers

Study Notes

Entity Characteristics

  • A strong entity has a unique existence, independent of other entities.
  • A weak entity, on the other hand, exists only in relation to another entity.

Entity Representation

  • A double underline in an entity box signifies a weak entity.

Relationships

  • Relationships link together entities.
  • A relationship with attributes becomes an associative entity when it has its own attributes.

Entity Definition

  • In the context of a database, an entity is an object or concept that has existence and can be described with a set of attributes.

Identifier (Key) Characteristics

  • An identifier (key) is a unique characteristic that distinguishes one entity from another.
  • Identifiers (keys) are differentiated from other attributes by being unique and non-null.

Attribute Characteristics

  • A composite attribute is made up of multiple simpler attributes.
  • A single-valued attribute implies that each entity instance has only one value for that attribute.

Identifier (Key) Purpose

  • The purpose of an identifier (key) is to uniquely identify each instance of an entity.

Relationship Descriptions

  • Features pertaining to the association between entities in a relationship are described by relationship attributes.

E-R Model Concepts

  • The degree of a relationship refers to the number of entities involved in the relationship.
  • A ternary relationship involves three different entity types related to each other.
  • One-to-Many cardinality means that one instance of an entity can be associated with multiple instances of another entity.
  • The participation constraint defines the minimum number of instances one entity can be associated with another in an E-R diagram.
  • A unary relationship involves only one entity type.
  • Multiple relationships are represented by multiple lines connecting entities in an E-R diagram.
  • Many-to-Many cardinality means that multiple instances of one entity can be associated with multiple instances of another entity.
  • The cardinality constraint specifies the maximum number of instances one entity can be associated with another in a relationship.

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Description

Test your understanding of objects in database modeling, focusing on instances in the database and attributes. Identify what should and should not be considered as entities in database modeling.

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