Podcast
Questions and Answers
In an Entity Relationship Diagram (ERD), what geometric shape is typically used to represent an entity?
In an Entity Relationship Diagram (ERD), what geometric shape is typically used to represent an entity?
- Rectangle (correct)
- Oval
- Diamond
- Circle
What does an Entity Relationship Diagram (ERD) primarily depict?
What does an Entity Relationship Diagram (ERD) primarily depict?
- The programming code used to access the database.
- The physical storage structure of a database.
- A conceptual representation of entities, attributes, and their relationships. (correct)
- The network architecture supporting the database system.
What is the term for a specific occurrence of an entity within an Entity Relationship Model (ERM)?
What is the term for a specific occurrence of an entity within an Entity Relationship Model (ERM)?
- Relationship occurrence
- Entity instance (correct)
- Attribute instance
- Entity set
What is the significance of capitalizing entity names in an Entity Relationship Diagram (ERD)?
What is the significance of capitalizing entity names in an Entity Relationship Diagram (ERD)?
In ER diagrams, how is the connectivity between entities represented?
In ER diagrams, how is the connectivity between entities represented?
What is the purpose of attributes in the context of an entity within a database model?
What is the purpose of attributes in the context of an entity within a database model?
Using Chen notation, how are attributes visually represented within an Entity Relationship Diagram (ERD)?
Using Chen notation, how are attributes visually represented within an Entity Relationship Diagram (ERD)?
In the Crow’s Foot notation, where are attributes written in relation to the entity rectangle?
In the Crow’s Foot notation, where are attributes written in relation to the entity rectangle?
In the Crow's Foot notation, what visual cue indicates that an attribute is required?
In the Crow's Foot notation, what visual cue indicates that an attribute is required?
What is the purpose of primary keys (PK) and foreign keys (FK) in the Crow's Foot notation?
What is the purpose of primary keys (PK) and foreign keys (FK) in the Crow's Foot notation?
If a relationship is named 'sings' between the entities 'SINGER' and 'SONG', which statement accurately reflects the implication within an ER model?
If a relationship is named 'sings' between the entities 'SINGER' and 'SONG', which statement accurately reflects the implication within an ER model?
When designing a database for a music library, which notation would best represent a one-to-many relationship between an 'ARTIST' and 'SONG'?
When designing a database for a music library, which notation would best represent a one-to-many relationship between an 'ARTIST' and 'SONG'?
In a database for a university, if each student is assigned to one specific department, what type of relationship exists between 'STUDENT' and 'DEPARTMENT'?
In a database for a university, if each student is assigned to one specific department, what type of relationship exists between 'STUDENT' and 'DEPARTMENT'?
In an ER diagram using Chen notation, if an oval representing an attribute is underlined, what does this indicate?
In an ER diagram using Chen notation, if an oval representing an attribute is underlined, what does this indicate?
In a library database, books are categorized into different genres. If one book can only belong to one genre, but each genre can contain multiple books, what relationship is accurately represented?
In a library database, books are categorized into different genres. If one book can only belong to one genre, but each genre can contain multiple books, what relationship is accurately represented?
When modeling a system where each employee is assigned a unique employee ID that cannot be null, which is the correct way to represent this in Crow’s Foot notation?
When modeling a system where each employee is assigned a unique employee ID that cannot be null, which is the correct way to represent this in Crow’s Foot notation?
Which of the following is true about entity names in ER diagrams, for clarity and consistency?
Which of the following is true about entity names in ER diagrams, for clarity and consistency?
In a scenario where a 'CUSTOMER' can place multiple 'ORDER's, and each 'ORDER' belongs to only one 'CUSTOMER', what cardinality is appropriate between 'CUSTOMER' and 'ORDER'?
In a scenario where a 'CUSTOMER' can place multiple 'ORDER's, and each 'ORDER' belongs to only one 'CUSTOMER', what cardinality is appropriate between 'CUSTOMER' and 'ORDER'?
In ER modeling, what does 'connectivity' refer to regarding relationships between entities?
In ER modeling, what does 'connectivity' refer to regarding relationships between entities?
What is the primary role of an Entity Relationship Model (ERM) in the context of databases?
What is the primary role of an Entity Relationship Model (ERM) in the context of databases?
Flashcards
Entity Relationship Model (ERM)
Entity Relationship Model (ERM)
A data model describing relationships among entities at a conceptual level.
Entity Relationship Diagram (ERD)
Entity Relationship Diagram (ERD)
A diagram depicting an entity relationship model's entities, attributes, and relations.
Entity (in ERD)
Entity (in ERD)
A diagram component representing a real-world object or subject.
Entity Instance
Entity Instance
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Entity Set
Entity Set
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Relationships (in ERD)
Relationships (in ERD)
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Connectivity
Connectivity
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Relationships describe..?
Relationships describe..?
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Attributes
Attributes
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Chen Notation
Chen Notation
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Crow's Foot Notation
Crow's Foot Notation
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Study Notes
- The Entity Relationship Model (ERM) is a data model describing relationships among entities at a conceptual level using ER diagrams.
- The Entity Relationship Diagram (ERD) depicts an entity relationship model's entities, attributes, and relations.
- Entities are represented in an ERD using rectangles (entity boxes) with the entity name (a noun) inside.
- Entity names should be in capital letters and singular form (e.g., SINGER, SONG).
- In a relational table, each row represents an entity instance or entity occurrence in the ER model.
- An entity set is a collection of similar entities.
- Relationships describe associations among data.
- Connectivity is the type of relationship between entities and is represented by a line in an ERD.
- Relationship names are active or passive verbs (e.g., SINGER sings SONGS).
ER Model Notations
- Relationships can be illustrated using Chen notation or Crow's Foot notation.
- Chen notation represents relationships with a diamond connected to entities via relationship lines, with the relationship name inside the diamond.
- Crow's Foot notation connects entities with lines and symbols describing the cardinality of the relationship.
Attributes
- Each entity has a set of attributes describing its characteristics.
- In Chen notation, attributes are represented by ovals connected to the entity rectangle, with the attribute name inside.
- The entity identifier is mapped as the table's primary key and is underlined.
- In Crow's Foot notation, attributes are in a box below the entity rectangle, with required attributes in bold.
- PK and FK are used to mark primary and foreign keys, respectively.
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