cHAPTER 1
d hoc query
A "spur-of-the-moment" question.
data dictionary
A DBMS component that stores metadata—data about data. Thus, the data dictionary contains the data definition as well as its characteristics and relationships. A data dictionary may also include data that are external to the DBMS. Also known as an information resource dictionary. See also active data dictionary, metadata, and passive data dictionary.
field
A character or group of characters (alphabetic or numeric) that defines a characteristic of a person, place, or thing. For example, a person's Social Security number, address, phone number, and bank balance all constitute fields.
record
A collection of related (logically connected) fields.
data inconsistency
A condition in which different versions of the same data yield different (inconsistent) results.
data redundancy
A condition that exists when a data environment contains redundant (unnecessarily duplicated) data.
data independence
A condition that exists when data access is unaffected by changes in the physical data storage characteristics.
data anomaly
A data abnormality that exists when inconsistent changes to a database have been made. For example, an employee moves, but the address change is corrected in only one file and not across all files in the database.
structural dependence
A data characteristic that exists when a change in the database schema affects data access, thus requiring changes in all access programs.
structural independence
A data characteristic that exists when changes in the database schema do not affect data access.
data dependence
A data condition in which the data representation and manipulation are dependent on the physical data storage characteristics.
transactional database
A database designed to keep track of the day-to-day transactions of an organization. See also production database.
centralized database
A database located at a single site.
operational database
A database that is designed primarily to support a company's day-to-day operations. Also known as a transactional database or production database.
multiuser database
A database that supports multiple concurrent users.
single-user database
A database that supports only one user at a time.
distributed database
A logically related database that is stored over two or more physically independent sites.
workgroup database
A multiuser database that supports a relatively small number of users (usually fewer than 50) or that is used for a specific department in an organization.
file
A named collection of related records.
query language
A nonprocedural language that is used by a DBMS to manipulate its data. An example of a query language is SQL.
Structured Query Language
A powerful and flexible relational database language composed of commands that enable users to create database and table structures, perform various types of data manipulation and data administration, and query the database to extract useful information.
data management
A process that focuses on data collection, storage, and retrieval. Common data management functions include addition, deletion, modification, and listing.
query
A question or task asked by an end user of a database in the form of SQL code. A specific request for data manipulation issued by the end user or the application to the DBMS.
database
A shared, integrated computer structure that houses a collection of related data. A database contains two types of data: end-user data (raw facts) and metadata. The metadata consist of data about data, that is, the data characteristics and relationships.
desktop database
A single-user database that runs on a personal computer.
islands of information
A term used in the old-style file system environment to refer to independent, often duplicated, and inconsistent data pools created and managed by different organizational departments.
performance tuning
Activities that make a database perform more efficiently in terms of storage and access speed.
database system
An organization of components that defines and regulates the collection, storage, management, and use of data in a database environment.
data warehouse
Bill Inmon, the acknowledged "father of the data warehouse," defines the term as "an integrated, subject-oriented, time-variant, nonvolatile collection of data that provides support for decision making."
metadata
Data about data, that is, data concerning data characteristics and relationships. See also data dictionary.
data integrity
In a relational database, refers to a condition in which the data in the database is in compliance with all entity and referential integrity constraints.
data
Raw facts, that is, facts that have not yet been processed to reveal their meaning to the end user.
database management system (DBMS)
Refers to the collection of programs that manages the database structure and controls access to the data stored in the database.
knowledge
The body of information and facts about a specific subject. Knowledge implies familiarity, awareness, and understanding of information as it applies to an environment. A key characteristic of knowledge is that "new" knowledge can be derived from "old" knowledge.
query result set
The collection of data rows that are returned by a query.
production database
The main database designed to keep track of the day-to-day operations of a company. See also transactional database.
enterprise database
The overall company data representation, which provides support for present and expected future needs.
database design
The process that yields the description of the database structure. The database design process determines the database components. Database design is the second phase of the database life cycle.
information
The result of processing raw data to reveal its meaning. Information consists of transformed data and facilitates decision making.
physical data format
The way in which a computer "sees" (stores) data.
logical data format
The way in which a human being views data.