13.2.2 Data modeling

• What does an entity represent in data modeling?

  A real-world object or concept
• Each entity in data modeling has attributes that describe its characteristics
• In a library system, a book is an example of an entity
• Match the entity with its attributes in a library system:

  Book ↔️ title, author, ISBN, publication date

  Member ↔️ name, address, membership number, phone number

  Loan ↔️ loan date, return date, loan status
• Why is identifying entities and their attributes crucial in database design?

  Defines data structure and organization
• Attributes are the characteristics that describe an entity
• What are the two components of an attribute?

  Name and data type
• The data type of an attribute ensures data is stored in the appropriate format
• Order the three main types of relationships in data modeling:

  1️⃣ One-to-One

  2️⃣ One-to-Many

  3️⃣ Many-to-Many
• What does a one-to-one relationship mean in data modeling?

  Each instance is related to one instance
• In a one-to-many relationship, each instance of the second entity is related to only one instance of the first
• In a many-to-many relationship, each instance of one entity can be related to multiple instances of another entity
• What is the primary purpose of an Entity-Relationship Diagram (ERD)?

  To visualize database structure
• Match the ERD component with its description:

  Entity ↔️ Rectangle representing real-world object

  Attribute ↔️ Oval connected to entities, describing characteristics

  Relationship ↔️ Diamond indicating how entities are related

  Relationship Type ↔️ Numerical notation showing the nature of the relationship
• What shape represents an entity in an ERD?

  Rectangle
• Numerical notations in an ERD show the nature of the relationship
• Entities in an ERD are represented by rectangles
• What shape represents an attribute in an ERD?

  Oval
• A many-to-many relationship is denoted as $1:n$ in an ERD.


  False
• What does a rectangle represent in an ERD?

  Entity
• What does a diamond represent in an ERD?

  Relationship
• Establishing relationships between entities is the second step in creating an ERD.
• Steps to create an ERD

  1️⃣ Identify the entities and their attributes

  2️⃣ Establish the relationships between entities
• Match the relationship type with its description:

  One-to-One ↔️ One instance of Entity A is related to only one instance of Entity B

  One-to-Many ↔️ One instance of Entity A is related to multiple instances of Entity B
• What is an Entity-Relationship Diagram (ERD)?

  Visual database structure representation
• To create an ERD, you first identify the entities
• Steps to create an ERD

  1️⃣ Identify entities and their attributes

  2️⃣ Establish relationships between entities
• What is a one-to-one relationship in an ERD?

  One instance relates to one
• In a one-to-many relationship, one instance of Entity A is related to multiple instances of Entity B
• What is a many-to-many relationship in an ERD?

  Multiple instances relate to multiple
• A one-to-one relationship means one instance of Entity A is related to exactly one instance of Entity B.
• What example is given for a one-to-many relationship in a library system ERD?

  Book and Loan
• Refining an ERD ensures it accurately represents the structure and relationships
• Refining an ERD improves data accuracy and reduces redundancy.
• What is the first key step in refining an ERD?

  Review entities and attributes
• Data redundancy in an ERD is reduced by applying normalization
• Steps to refine an ERD

  1️⃣ Ensure data integrity

  2️⃣ Validate with stakeholders
• What is missing in the Loan entity before refining in the library system example?

  Return condition
• The "return condition" attribute is added to the Loan entity after refining the ERD.
• Steps in refining an ERD

  1️⃣ Review Entities and Attributes

  2️⃣ Examine Relationships

  3️⃣ Normalize Data

  4️⃣ Ensure Data Integrity

  5️⃣ Validate with Stakeholders