CTEC 226 Ch. 2

Normalization

A process of analyzing a relation to ensure that it is well formed.

Fourth Normal Form (4NF)

A relation in BCNF in which every multivalued dependency is a functional dependency

Second Normal Form (2NF)

A relation in first normal form in which all non-key attributes are dependent on all the keys.

Third Normal Form (3NF)

A relation in second normal form that has no transitive dependencies.

Boyce-Codd Normal Form (BCNF)

A relation in third normal form in which every determinant is a candidate key

Domain Key/Normal Form (DK/NF)

A relation in which all constraints are logical consequences of domains and keys. In this text, this definition has been simplified to a relation in which the determinants of all functional dependencies are candidate keys.

Functional Dependency

A relationship between attributes on which one attribute (or group of attributes) determines the value of another attribute in the same table

Referential Integrity Constraint

A relationship constraint on foreign key values. A referential integrity constraint specifies that the values of a foreign key must be a proper subset of the values of the primary key to which it refers. States that every value of a foreign key must match a value of an existing primary key

Record

(1) A group of field pertaining to the same entity; used in file-processing systems (2) In the relational model, a synonym for row and tuple.

Relation

A two-dimensional table that has specific characteristics - consists of rows & columns. No duplicate rows

Surrogate Key

A unique, numeric value that is added to a relation to serve as the primary key - Values have no meaning to users and are usually hidden on forms, queries, and reports - A surrogate key is often used in place of a composite primary key

Candidate Key

An attribute or a group of attributes that identifies a unique row in a relation. One of the _____________________ is chosen to be the primary key. It's a candidate to become a primary key - a _________________ is a unique key

First Normal Form (1NF)

Any table that fits the definition of a relation

Transitive Dependency

In a relation having at least three attributes

Entity

Something of importance to a user that needs to be represented in a database. It represents one theme or topic

Normalization Process

The process of evaluating a relation to determine whether it is in a specified normal form and, if necessary, of converting it to relations in that specified normal form.

Tuple

aka Row

Primary Key

A candidate key chosen to be the main key for the relation

Database Schema

A complete logical view of a database

Multivalued Dependency

A condition in a relation with three or more attributes in which independent attributes appear to have relationships they do not have.

Table

A database structure of rows and columns to create cells that hold data values. Also known as a relation in a relational database, although strictly only tables that meet specific conditions can be called relations.

Row

A group of columns in a table. All the columns in a row pertain to the same entity. Also known as Tuple or Record.

Key

A group of one or more attributes that identify a unique row in a relation.

Determinant

One or more attributes that functionally determine another attribute or attributes. Functional Dependency The attribute (or attributes) that we use as the starting point (the variable on the left side of the equation).

Composite Key

A key that contains two or more attributes/columns - For a key to be unique it must often become a ____________________

Unique Key

A key that identifies a unique row

Nonunique Key

A key that potentially identifies more than one row

Column

A logical group of bytes in a row of a relation or a table. The meaning of a column is the same for every row of the relation.

Field

(1) A logical group of bytes in a record used with file processing (2) In the context of the relational model, a synonym for attribute

Attribute

(1) A value that represents a characteristic of an entity. (2) A column of a relation

Fifth Normal Form (5NF)

A normal form necessary to eliminate an anomaly where a table can be split apart but not correctly joined back together. Also known as Project Join Normal Form.

Foreign Key

An attribute that is a key of one or more relations other than the one in which it appears. May need to create a foreign key in order to preserve relationships A primary key from one table placed into another table

Null Value

An attribute value that has never been supplied. Such values are ambiguous and can mean the value is unknown, the value is not appropriate, or the value is known to be blank. Means that no data was entered. - Different from a zero, space character, or tab character