Systems Chapter 9

Recursive Foreign Key P 327

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

Physical Table P 336

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

Physical file P 338

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

Relation P 319

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

Third Normal form (3NF) P 322

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

Second Normal form (2NF) P 322

A relation is in second normal form if every nonprimary key attribute is functionally dpependent on the whole primary key.

Well-structured relation P 320

A relation the contains a minimum amount of redundancy nd that allows users to insert, modify, and delete the rows without error or inconsistencies, also known as a table.

Referential Integrity P 323

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

Denormalization P 336

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

Field P 333

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

Synonym P 329

Two different names that are used for the same attribute.

Data Type P 333

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

Function dependency P 321

A constrain between two attributes in which the value of one attribute is determines by the value of another attribute.

Pointer P 339

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

Calculated Field P 334

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

Indexed file organization

A file organization in which rows are stored either sequentially or nonsequentially and an index is created that allows software to locate individual rows.

Sequential File Organization P 340

A file organization in which rows in a file are stored in sequence according to a primary key value.

Hashed File Organization

A file organization in which the address of each row is determined using an algorithm.

Homonym P 329

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

null value P 335

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

File organization P 338

A technique for physically arranging the records of a file.

Default value P 335

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

Normalization P 315

A way to build a data model that has the properties of simplicity, nonredundancy, and minimal maintenance.

Primary Key P 316

An attribute (or combination of attributes) whose value is unique across all occurences of a relation.

Foreign Key P 323

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

Relational Database model P 319

Data represented as a set of related tables or relations.

Secondary Key P 340

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

Normalization P 321

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