Unit 7 : Entity Relationship Model ( Part 2 )

Question 1

What is optional participation in a relationship?

Answer 1

1. Means one entity occurrence does not require a corresponding entity occurrence in a particular relationship.

• A customer may have zero or more orders, meaning the relationship between the customer and orders is optiona

Question 2

What is mandatory participation in a relationship?

Answer 2

1. Mans one entity occurrence requires a corresponding entity occurrence in a particular relationship.

• A student must be enrolled in at least one course, meaning the relationship between the student and course is mandatory.

Question 3

What does relationship participation refers to?

Answer 3

1. Refers to how entities participate in a relationship in a database model, especially in the context of an Entity-Relationship (ER) diagram.

Question 4

Can an entity with optional participation exist without being part of a relationship?

Answer 4

Yes, an entity with optional participation can exist without being part of a relationship.

Question 5

What does the degree of relationship indicates?

Answer 5

1. Number of entities or participants associated with a relationship

Question 6

List out all the 4 relationship in relationship degree

Answer 6

1. Unary Relationship
2. Binary Relationship
3. Ternary Relationship
4. Quaternary Relationship

Question 7

What is unary relationship?

Answer 7

1. Association is mainteined within single entry

• An employee manages another employee (relationship within the same entity “Employee”).

Question 8

What is binary relationship?

Answer 8

1. Two entities are associated

• A customer places an order (relationship between “Customer” and “Order”).

Question 9

What is ternary relationship?

Answer 9

1. Three entities are associated

• A supplier provides a product to a warehouse (relationship among “Supplier,” “Product,” and “Warehouse”)

Question 10

What is quaternary relationship?

Answer 10

1. Four entities are associated

• A project involves an employee, client, department, and supervisor (relationship among “Project,” “Employee,” “Client,” and “Department”)

Question 11

What is a recursive relationship?

Answer 11

1. Relationship exist between occurrences of the same entity set

• An employee supervises another employee. Both are part of the same entity set “Employee.”

Question 12

Where are recursive relationships typically found?

Answer 12

1. Naturally found within unary relationship

Question 13

Can you have a recursive relationship in a binary or ternary relationship?

Answer 13

1. No, recursive relationships are specific to unary relationships where one entity type relates to itself.

Question 14

What type of relationship involves an entity relating to itself?

Answer 14

1. A unary relationship, where an entity is associated with itself.

Question 15

What is composite entities also known as?

Answer 15

1. Bridge entities

Question 16

What is composite entities?

Answer 16

1. Composed of primary keys of each of the entities to be connected

Question 17

Can composite entities contain attributes?

Answer 17

1. Yes , but may only contain additional attributes that play no role in connective process