Chapter 9 Designing Databases

A field that can be derived from other database fields.

Calculated Field

A coding scheme recognized by system software for representing organizational data.

Data Type

A value a field will assume unless an explicit value is entered for that field.

Default Value

The process of splitting or combining normalized relations into physical tables based on affinity of use of rows and fields.

Denormalization

The smallest unit of named application data recognized by system software.

Field

A technique for physically arranging the records of a file.

File Organization

An attribute that appears as a non-primary key attribute in one relation and as a primary key attribute (or part of a primary key) in another relation.

Foreign Key

A particular relationship between two attributes.

Functional Dependency

The address for each row is determined using an algorithm.

Hashed File Organization

A single attribute named that is used for two or more different attributes.

Homonym

A table used to determine the location of rows in a file that satisfy some condition.

Index

The rows are stored either sequentially or non-sequentially, and an index is created that allows software to locate individual rows.

Indexed File Organization

The process of converting complex data structures into simple, stable data structures.

Normalization

A special field value, distinct from a zero, blank, or any other value, that indicates that the value for the field is missing or otherwise unknown.

Null Value

A named set of table rows stored in a contiguous section of secondary memory.

Physical File

A named set of rows and columns that specifies the fields in each row of the table.

Physical Table

A field of data that can be used to locate a related field or row of data.

Pointer

An attribute whose value is unique across all occurrences of a relation.

Primary Key

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

Recursive Foreign Key

An integrity constraint specifying that the value (or existence) of an attribute in one relation depends on the value (or existence) of the same attribute in another relation.

Referential Intergrity

A named, two dimensional table of data. Each relation consists of a set of named columns and an arbitrary number of unnamed rows.

Relation

Data represented as a set of related tables or relations.

Relational Database Model

A relation for which every non-primary key attribute is functionally dependent on the whole primary key.

Second Normal Form

One or a combination of fields for which more than one row may have the same combination of values.

Secondary Key

The rows in the file are stored in a sequence according to a primary key value.

Sequential File Organization

Two different names that are used for the same attribute.

Synonym

A relation that is in second normal form and that has no functional (transitive) dependencies between two (or more) non-primary key attributes.

Third Normal Form

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

Well-Structured Relation