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Questions and Answers
What is the term used to describe a relationship type of degree two?
What is the term used to describe a relationship type of degree two?
What is the degree of a ternary relationship type?
What is the degree of a ternary relationship type?
What is the role of an entity type in a relationship type?
What is the role of an entity type in a relationship type?
What is the minimum number of entity types required to form a relationship type?
What is the minimum number of entity types required to form a relationship type?
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What is the term used to describe a relationship type of degree one?
What is the term used to describe a relationship type of degree one?
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How many entity types are involved in a quaternary relationship type?
How many entity types are involved in a quaternary relationship type?
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Study Notes
Entity and Relationship Constraints
- A tuple in R is uniquely identified by the values of K, which is known as uniqueness.
- No proper subset of K has the uniqueness property, which is known as irreducibility.
- A composite key is a key that consists of more than one attribute.
Primary Key
- A primary key is a candidate key that is selected to uniquely identify tuples within a relation.
General Constraints
- General constraints are additional rules specified by users or database administrators to define or constrain aspects of the enterprise.
Entity Set
- An entity set, also known as the extension of an entity type, is a collection of entities of a particular entity type.
Entity Type
- Key attributes of an entity type define the characteristics of an entity.
- Example: An employee is assigned to one department but may work on several projects, which are not necessarily controlled by the same department.
Relationship Types
- A relationship type of degree two is called binary.
- A relationship type of degree three is called ternary.
- Each entity type that participates in a relationship type plays a particular role in the relationship.
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Description
Learn about the properties of keys in database management systems, including uniqueness, irreducibility, and composite keys. Understand the role of primary keys in identifying tuples.
