Database Reference
In-Depth Information
Markup language
A document language that contains
tags that describe a document's content and appearance.
Message
A request to execute a method. Also, data,
requests, or responses sent from one computer to
another computer on a network.
Metadata
Data about the data in a database.
Metalanguage
A language used to define another
language.
Method
An action defined for a object class.
Minor sort key
See secondary sort key.
Multidependent
In a table with columns A, B, and C, B
is multidependent on A if each value for A is associated
with a specific collection of values for B and, further,
this collection is independent of any values for C.
Multidetermine
In a table with columns A, B, and C, A
multidetermines B if each value for A is associated with
a specific collection of values for B and, further, this
collection is independent of any values for C.
Multidimensional database
The perceived structure by
users of the data in a data warehouse.
Multiple-column index
See multiple-field index.
Multiple-field index
An index built on more than one
field (column).
Multiplicity
In UML, the number of objects that can be
related to an individual object on the other side of a
relationship; also called cardinality.
Multivalued dependence
In a table with columns A, B,
and C, there is a multivalued dependence of column B
on column A (also read as “B is multidependent on A” or
“A multidetermines B”), if each value for A is associated
with a specific collection of values for B and, further-
more, this collection is independent of any values for C.
Natural join
The most common form of a join.
Natural key
A primary key that consists of a column or
collection of columns that is an inherent characteristic
of the entity.
Navigation form
A form in a database or a Web data-
base that contains a navigation control that lets a user
access different objects in a database.
Network
See communications network.
Nonidentifying relationship
A relationship that is not
necessary for identification.
Nonkey attribute
See nonkey column.
Nonkey column
An attribute (column) that is not part
of the primary key.
Nonprocedural language
A language in which a user
describes the task that is to be accomplished by the
computer rather than the steps that are required to
accomplish it.
Normal form
See first normal form, second normal
form, third normal form, and fourth normal form.
Normalization process
The process of removing
repeating groups to produce a first normal form table.
Sometimes refers to the process of creating a third nor-
mal form table.
n-tier architecture
See three-tier architecture.
Null
A data value meaning “unknown” or “not
applicable.”
Object
A unit of data (set of related attributes) along
with the actions that are associated with that data.
Object-oriented database management system
(OODBMS)
A DBMS in which data and the methods
that operate on that data are encapsulated into objects.
Office Open XML
A Microsoft file format that is a
compressed version of XML and first used in the Office
2007 suite.
OLAP
See online analytical processing.
OLTP
See online transaction processing.
One-to-many relationship
A relationship between two
entities in which each occurrence of the first entity is
related to many occurrences of the second entity, and
each occurrence of the second entity is related to at
most one occurrence of the first entity.
One-to-one relationship
A relationship between two
entities in which each occurrence of the first entity is
related to one occurrence of the second entity, and each
occurrence of the second entity is related to at most one
occurrence of the first entity.
Online analytical processing (OLAP)
Software that is
optimized to work efficiently with multidimensional
databases in a data warehouse environment.
Online transaction processing (OLTP)
A system that
processes a transaction by dealing with a small number
of rows in a relational database in a highly structured,
repetitive, and predetermined way.
OODBMS
See object-oriented database management
system.
Optional role
The role in a relationship played by an
entity with a minimum cardinality of zero (that is, there
need not be any occurrences of the entity).
OR criterion
A combination of criteria in which at least
one of the criteria must be true.
ORDER BY clause
The part of an SQL SELECT com-
mand that indicates a sort order.
Outer join
The form of a join in which all records
appear, even if they don't match.
Partial dependency
A dependency of a column on only
a portion of the primary key.
Password
A string of characters assigned by a DBA to a
user that the user must enter to access a database.
Patriot Act
A federal law enacted in 2001 that specifies
data retention requirements for the identification of
customers opening accounts at financial institutions,
allows law enforcement agencies to search companies'
and individuals' records and communications, and
expands the government's authority to regulate financial
transactions.
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