CPS 430 Final
What is a Derived Attribute?
An attribute whose value can be derived (computed) from another attribute.
What is a Multivalued Attribute?
An attribute with a set of values for a single entity.
What is a Weak Entity?
An entity that can be identified uniquely only by considering the primary key of another (owner) entity.
What is a Participation Constraint?
A constraint that specifies the number of instances that an entity can participate in a relationship set.
What is a Cardinality Constraint?
A constraint that specifies the number of relationship instances that an entity can participate in.
What is the Update Anomaly?
A data inconsistency that results from data redundancy and a partial update.
What is an Attribute?
A property of an entity.
What is a Functional Dependency in a database?
A property of the semantics of the other attributes (how they relate to one another).
What are Entities?
A real-world object that is distinguishable from other objects.
What is an Identifying Relationship?
A relationship that relates a weak entity to its owner.
What are the formal properties of a good database design?
All attributes are preserved (from the real world application the database is modeling). All dependencies are preserved. All relations are in 3rd normal form (at least). All joins are lossless.
What are the informal properties of a good database design?
All attributes in a relation should have a clear meaning. Reduce redundant information in tuples (update anomalies). Reduce nulls in tuples. Prevent spurious tuples.
How can you tell if a database is in First Normal Form?
All columns contain atomic values only. All occurrences have the same number of columns. Attributes must have a single value. (Every relational database is in this form by definition)
What is a Relationship?
An association among two or more entities.
What is a Key Attribute?
An attribute (or set of attributes) for an entity whose values are unique for each instance of the entity.
What is a Simple Attribute?
An attribute that can not be subdivided.
What is a Composite Attribute?
An attribute that is composed of several more basic attributes.
How can you tell if a database is in Second Normal Form?
If every nonprime attribute is fully functionally dependent on the primary key.
What anomalies may occur if a database is not in third normal form?
Insert, Update, and Delete.
What is an Existence Dependency?
It describes whether an entity in a relationship is optional or mandatory.
What are the three levels of database architecture?
The Internal level, the Conceptual level, and the External/View level.
How can you tell if a database is in Third Normal Form?
The database is in 2NF No nonprime attribute is transitively dependent on the primary key.
What is Closure?
The full set of attributes that can be determined from a set of known attributes, for a given database, using functional dependencies.
What is the Insert Anomaly?
The inability to add data to the database due to the absence of other data.
What is the Delete Anomaly?
The inability to remove data from the table without having to delete the entire record.
What is the External/View level of database architecture?
The level of database architecture that describes the database view for one group of database users.
What is the Internal level of database architecture?
The level of database architecture that describes the physical storage structure of a database.
What is the Conceptual level of database architecture?
The level of database architecture that describes the structure of an entire database for the community of users and describes the entities, data types, relationships, and constraints of the database.
What is Mapping?
The process of transforming requests and results between levels.
What is the process of a user request through database architecture?
The request is specified on the external schema into a request on the conceptual schema, then into a request on the internal schema for stored database processing.