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Questions and Answers
Which attribute can have multiple values?
Which attribute can have multiple values?
A composite attribute cannot be subdivided.
A composite attribute cannot be subdivided.
False
What is a derived attribute?
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' __________.
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' __________.
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Match the following attribute types to their definitions:
Match the following attribute types to their definitions:
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Which of the following is true about single-value attributes?
Which of the following is true about single-value attributes?
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Derived attributes must always be stored physically in the database.
Derived attributes must always be stored physically in the database.
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What should be done instead of implementing multivalued attributes in M:N relationships?
What should be done instead of implementing multivalued attributes in M:N relationships?
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What does an Entity Relationship Diagram (ERD) primarily represent?
What does an Entity Relationship Diagram (ERD) primarily represent?
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An entity in the context of ER modeling refers to a single occurrence of data.
An entity in the context of ER modeling refers to a single occurrence of data.
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What shape is used to represent an entity in the Chen and Crow's Foot models?
What shape is used to represent an entity in the Chen and Crow's Foot models?
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In an ERD, the name of an entity is written in ______ letters.
In an ERD, the name of an entity is written in ______ letters.
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Which of the following components is NOT a main part of an ERD?
Which of the following components is NOT a main part of an ERD?
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Conflicting goals in real-world database design are rare and easily reconciled.
Conflicting goals in real-world database design are rare and easily reconciled.
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What term is used to describe the connections between entities in an ERD?
What term is used to describe the connections between entities in an ERD?
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Match the following terms with their descriptions:
Match the following terms with their descriptions:
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What type of relationship exists between occurrences of the same entity set?
What type of relationship exists between occurrences of the same entity set?
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Associative entities are also known as bridge entities.
Associative entities are also known as bridge entities.
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What is the primary purpose of associative entities?
What is the primary purpose of associative entities?
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An associative entity is composed of the primary keys of __________ entities to be connected.
An associative entity is composed of the primary keys of __________ entities to be connected.
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What can an associative entity contain besides primary keys?
What can an associative entity contain besides primary keys?
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Unary relationships can occur only between two different entity sets.
Unary relationships can occur only between two different entity sets.
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What is another term for an associative entity?
What is another term for an associative entity?
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What type of relationship requires that one entity occurrence must correspond to a specific entity occurrence?
What type of relationship requires that one entity occurrence must correspond to a specific entity occurrence?
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A unary relationship involves three entities.
A unary relationship involves three entities.
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What does the degree of a relationship indicate?
What does the degree of a relationship indicate?
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In a ______ relationship, two entities are associated.
In a ______ relationship, two entities are associated.
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Match the type of relationship with its definition:
Match the type of relationship with its definition:
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Which of the following statements is TRUE regarding optional participation?
Which of the following statements is TRUE regarding optional participation?
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A ternary relationship involves two associated entities.
A ternary relationship involves two associated entities.
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What type of relationship does not require a corresponding entity occurrence?
What type of relationship does not require a corresponding entity occurrence?
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What type of relationship exists if the primary key of the related entity does not contain a primary key component of the parent entity?
What type of relationship exists if the primary key of the related entity does not contain a primary key component of the parent entity?
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A weak entity has its primary key totally independent of the parent entity.
A weak entity has its primary key totally independent of the parent entity.
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What two conditions must a weak entity meet?
What two conditions must a weak entity meet?
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A strong relationship exists when the PK of the related entity contains the ___ component of the parent entity.
A strong relationship exists when the PK of the related entity contains the ___ component of the parent entity.
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Which of the following best describes a weak entity?
Which of the following best describes a weak entity?
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The classification of an entity as weak is solely determined by its primary key.
The classification of an entity as weak is solely determined by its primary key.
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The classification of a weak entity is influenced by ___ rules.
The classification of a weak entity is influenced by ___ rules.
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What is NOT a typical conflicting goal for database designers?
What is NOT a typical conflicting goal for database designers?
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An entity relationship model (ERM) must always represent the actual database structure exactly as implemented.
An entity relationship model (ERM) must always represent the actual database structure exactly as implemented.
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Name the main components of an entity relationship model (ERM).
Name the main components of an entity relationship model (ERM).
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A M:N relationship must be mapped to a set of ______ relationships.
A M:N relationship must be mapped to a set of ______ relationships.
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Match the following terms with their correct descriptions:
Match the following terms with their correct descriptions:
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Which of the following is a key factor database designers must consider when designing databases?
Which of the following is a key factor database designers must consider when designing databases?
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Connectivity in an ERD only refers to the number of entities involved.
Connectivity in an ERD only refers to the number of entities involved.
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What diagram is used to represent the static data structures in a data model?
What diagram is used to represent the static data structures in a data model?
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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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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.
