Podcast
Questions and Answers
What is a relationship in the context of entity modeling?
What is a relationship in the context of entity modeling?
- A one-directional association between two entities
- A connection between multiple entities with no significance to the business
- An attribute of an entity that describes its characteristics
- A two-directional, significant association between two entities or between an entity and itself (correct)
What are the components that describe a relationship?
What are the components that describe a relationship?
- Association, linkage, and connection
- Entity, attribute, and value
- -abstraction, instance, and participant
- Name, optionality, and degree (correct)
What is an example of a relationship between entities?
What is an example of a relationship between entities?
- Employees have skills
- Employees are assigned to projects (correct)
- Projects have departments
- Departments are managed by employees
What is a relationship type in the context of entity modeling?
What is a relationship type in the context of entity modeling?
What are the entities involved in a relationship called?
What are the entities involved in a relationship called?
What is total participation in the context of entity relationships?
What is total participation in the context of entity relationships?
What is the purpose of assigning a name, optionality, and degree to a relationship?
What is the purpose of assigning a name, optionality, and degree to a relationship?
What is the significance of a relationship in the context of entity modeling?
What is the significance of a relationship in the context of entity modeling?
What is an example of a relationship instance?
What is an example of a relationship instance?
What is the nature of a relationship between entities?
What is the nature of a relationship between entities?
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Study Notes
Relationships in Entity-Relationship Modeling
- A relationship is an association, linkage, or connection between two or more entities of interest to the business.
- A relationship is two-directional and has a name, optionality (optional or mandatory), and a degree (how many).
- Relationships represent associations between two or more entity instances.
Relationship Characteristics
- Each relationship has a name, which helps confirm its validity.
- Optionality (optional or mandatory) defines whether an entity must participate in the relationship.
- Degree (how many) defines the number of entities involved in the relationship.
Types of Relationships
- Relationship type is an abstraction of a relationship, representing a set of relationship instances sharing common attributes.
Participation in Relationships
- Entities enrolled in a relationship are called its participants.
- Participation of an entity in a relationship can be total (all entities participate) or partial (not all entities participate).
Naming Relationships
- Relationships can be named using a descriptive phrase or abbreviations of participant names.
- Example: STUDENT and CLASS have an ENROLL relationship, which can also be named as STD_CLS.
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