Chapter 9 MIS Test 2

Physical Table

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

Relation

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

Second Normal Form (2NF)

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

Hashed File Organization

The address for each row is determined using an algorithm

Denormalization

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

Field

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

Synonym

Two different names that are used for the same attribute.

Calculated Field

A field that can be derived from other database fields. Also known as a computed field or a derived field.

Physical File

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

Indexed file organization

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

Recursive foreign key

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

Functional dependency

A particular relationship between two attributes.

Well-Structured Relation

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

Third normal form (3NF)

A relation that is in second normal form that has no function (transitive) dependencies between two (or more) nonprimary key attributes.

Null Value

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.

Primary Key

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

Referential Integrity

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

Data type

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

Pointer

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

Homonym

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

Index

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

File Organization

A technique for physically arranging the records of a file.

Default Value

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

Foreign Key

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

Relational Database Model

Data represented as a set of related tables or relations.

Secondary Key

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

Normalization

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

Sequential file organization

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