What is entity Supertype and why is it used?
An entity supertype is a generic entity type that is related to one or more entity subtypes, where the entity supertype contains the common characteristics and the entity subtypes contain the unique characteristics of each entity subtype. The reason for using supertypes is to minimize the number of nulls.
What are an entity cluster and what advantages are derived from its use?
It is a virtual entity which gives benefit to present the multiple entities and relationship in the ERD. An Entity cluster is used to combine the multiple entities and relationship which relate each other into a single entity. It is also used to simplify the ERD and increasing its readability features.
What is entity supertype?
A supertype is a generic entity type that has a relationship with one or more subtypes. A subtype is a sub-grouping of the entities in an entity type that is meaningful to the organization and that shares common attributes or relationships distinct from other subgroups.
What is a specialization hierarchy?
specialization hierarchy. A hierarchy based on the top-down process of identifying lower-level, more specific entity subtypes from a higher-level entity supertype. Specialization is based on grouping unique characteristics and relationships of the subtypes.
What is time variant data and how would you deal with such data from a database design point of view?
– Time variant data is time-sensitive. For example, if a university wants to keep track of the history of all administrative appointments by date of appointment and date of termination, you see time-variant data at work.
What are examples of entities?
Examples of an entity are a single person, single product, or single organization. Entity type. A person, organization, object type, or concept about which information is stored. Describes the type of the information that is being mastered.
What is entity subtype?
An entity subtype is a more specific entity type that is related to an entity supertype, where the entity supertype contains the common characteristics and the entity subtypes contain the unique characteristics of each entity subtype.
What is a discriminator attribute?
A subtype discriminator is an attribute of the supertype that indicates an entity’s subtype. The attribute’s values are what determine the target subtype. Disjoint subtypes – simple attributes that must have alternative values to indicate any possible subtypes.
What is a Specialised entity?
The subordinated (“specialized”) entity type is a subset of the superior (“generalized“) entity type; it inherits the attributes and relationship types of the “generalized“ entity type. A specialized entity type, however, may have attributes and relationship types of its own.
What is an entity Supertype and why is it used quizlet?
What is an entity supertype, and why is it used? An entity supertype is a generic entity type that is related to one or more entity subtypes, where the entity supertype contains the common characteristics and the entity subtypes contain the unique characteristics of each entity subtype.