Chapter Four - Business Data Management

Relation

A named two-dimensional table of data

Null

A value that may be assigned to an attribute when no other value applies or when the applicable value is unknown

False

T/F A composite key consists of only one attribute

False

T/F The truncate table statement in SQL creates a new table

Composite Key

A primary key that consists of more than one attribute

True

T/F A primary key is an attribute that uniquely identifies each row in a relation

False

T/F When transforming a unary many-to-many relationship to relations, a recursive foreign key is used

False

T/F When transforming a weak entity, one should create one relation with both the attributes of the strong entity and the attributes of the weak entity

Determinant

The attribute on the left side of the arrow in a functional dependency

Alias

An alternative name used for an attribute

False

T/F A foreign key is a primary key of a relation that also is a primary key in another relation

False

T/F In the relational data model, associations between tables are defined through the use of primary keys

Normalization

The process of decomposing relations with anomalies to produce smaller, well-structured relations.

Synonyms

Two (or more) attributes that have different names but the same meaning.

Functional Dependency

A constraint between two attributes in which the value of one attribute is determined by the value of another attribute

Recursive foreign key

A foreign key in a relation that references the primary key values of the same relation

Transitive dependency

A functional dependency between the primary key and one or more nonkey attributes that are dependent on the primary key via another nonkey attribute

Partial functional dependency

A functional dependency in chi one or more nonkey attributes are functionally dependent on part (but not all) of the primary key.

Second normal form (2NF)

A relation in first normal form in which every nonkey attribute is fully functionally dependent on the primary key.

Well-structured relation

A relation that contains minimal redundancy and allows users to insert, modify, and delete the rows in a table without errors or inconsistencies.

First Normal Form (1NF)

A relation that has a primary key an in which there are no repeating groups

Third normal form (3NF)

A relation that is in second normal form and has not transitive dependencies

Referential integrity constraint

A rule that states that either each foreign key value must match a primary key value in another relation or the foreign key value must be null

Entity Integrity Rule

A rule that states that no primary key (or component of a primary key attribute) may be null

Surrogate primary key

A serial number or other system-assigned primary key for a relation

Normal form

A state of a relation that requires that certain rules regarding relationship between attributes (or functional dependencies) are satisfied

Foreign Key

An attribute in a relation that serves as the primary key of another relation in the same database

Primary key

An attribute or a combination of attributes that uniquely identifies each row in a relation

Homonym

An attribute that may have more than one meaning

Candidate Key

An attribute, or combination of attributes, that uniquely identifies a row in a relation

Anomaly

An error or inconsistency that may result when a user attempts to update a table that contains redundant data. The three types of anomalies are insertion, deletion, and modification anomalies

True

T/F A candidate key is an attribute, or combination of attributes, that uniquely identifies a row in a relation

True

T/F A cascading delete removes all records in other tables associated with the record to be deleted

True

T/F A partial functional dependency is a functional dependency in which one or more non key attributes are functionally dependent on part (but not all) of the primary key

True

T/F A referential integrity constraint is a rule that maintains consistency among the rows of two relations

False

T/F A relation is in first normal form if it has no more than one multivalued attribute

False

T/F A transversal dependency is a functional dependency between two or more nonkey attributes

True

T/F A well-structured relation contains minimal redundancy and allows users to manipulate the relation without errors or inconsistencies

True

T/F All values that appear in a column of a relation must be taken from the same domain

False

T/F CASE tools can model more complex data relationships, such as ternary relationships

False

T/F Data integrity consists of powerful operations to manipulate data stored in relations

True

T/F Data structures include data organized in the form of tables with rows and columns

True

T/F If an identifier is not assigned, the default primary key for an associative relation consists of the two primary key attributes from the other two relations

True

T/F One property of a relation is that each attribute within a relation has a unique name

True

T/F The allowable range of values for a given attribute is part of the domain constraint

False

T/F The entity integrity rule states that a primary key attribute can be null

False

T/F The primary key of the many side migrates to the one side when transforming a one-to-many relationship

False

T/F The relational data model does, at this time, directly support subtype/supertype relationships

False

T/F There can be multivalued attributes in a relation

False

T/F Unlike columns, the rows of a relation may not be interchanged and must be stored in one sequence

True

T/F View integration is the process of merging relations together

True

T/F When a regular entity type contains a multivalued attribute, two relations are created

True

T/F When normalizing, the goal is to decompose relations with anomalies to produce smaller, well-structure relations.

False

T/F When transforming a one-to-one relationship, a new relation is always created