Exam 5: Advanced Data Modeling

Entity subtypes do not inherit the relationships in which the supertype entity participates.

In the context of total completeness, in a(n) , every supertype occurrence is a member of at least one subtype.

data refer to data whose values change over time and for which one must keep a history of the data changes.

One practical advantage of a(n) key is that because it has no intrinsic meaning, values for it can be generated by the DBMS to ensure that unique values are always provided.

Describe an entity cluster.

While using a surrogate key, one must ensure that the candidate key of the entity in question performs properly through the use of the " " and "not null" constraints.

In which two cases are composite primary keys particularly useful?

The completeness constraint can be partial or total.

If one exists, a data modeler uses a as the primary key of the entity being modeled.

The preferred placement for a foreign key when working with a 1:1 relationship is to .

The relationships depicted within the specialization hierarchy are sometimes described in terms of "is-a" relationships.

The property of a subtype discriminator enables an entity supertype to inherit the attributes and relationships of the subtype.

Differentiate between specialization and generalization.

completeness means that every supertype occurrence must be a member of at least one subtype.

Implementing nonoverlapping subtypes requires the use of one discriminator attribute for each subtype.

Generalization is based on grouping unique characteristics and relationships of the subtypes.

One important inheritance characteristic is that all entity subtypes inherit their key attribute from their supertype.

Nonoverlapping subtypes are subtypes that contain a(n) subset of the supertype entity set.

The " " characteristic of a primary key states that the primary key must uniquely identify each entity instance, must be able to guarantee unique values, and must not contain nulls.

An entity cluster is considered "virtual" or " " in the sense that it is not actually an entity in the final ERD.