-Person, place, object, event, concept, etc. (Noun) Show
-Entity type vs. entity instance (Table vs. Row) type: should be: -An object that will be composed of multiple attributes -An object that we are trying to model Should not be: -An output of the database system (e.g., a report) What are characteristics or properties of an entity called?Attribute. A characteristic or trait of an entity type that describes the entity, for example, the Person entity type has the Date of Birth attribute.
What term would you use to describe a group of entities that share common characteristics or properties?Answer: An entity type is a collection of entities that share common properties. An entity instance is a single occurrence of an entity type. So, for example, STUDENT is an entity type and John Smith is an entity instance.
Is an attribute that uniquely identifies individual instances of an entity type?The primary key is an attribute or a set of attributes that uniquely identify a specific instance of an entity. Every entity in the data model must have a primary key whose values uniquely identify instances of the entity.
What is the number of entity types that participate in that relationship?Cardinality: The number of times an entity of an entity set participates in a relationship set is known as cardinality.
|
A property or characteristic of an entity type that is of interest to the organization is called
zusammenhängende Posts
Urheberrechte © © 2024 membukakan Inc.
