study guide Flashcards
ad hoc query
A “spur-of-the-moment” question.
centralized database
A database located at a single site.
data
Raw facts, that is, facts that have not yet been processed to reveal their
meaning to the end user.
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.
data dependence
A data condition in which the data representation and
manipulation are dependent on the physical data storage characteristics.
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.
data inconsistency
A condition in which different versions of the same data yield different (inconsistent) results.
data independence
A condition that exists when data access is unaffected by changes in the physical data storage characteristics.
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 management
A process that focuses on data collection, storage, and retrieval. Common data management functions include addition, deletion, modification, and listing.
data redundancy
A condition that exists when a data environment contains redundant (unnecessarily duplicated) data.
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.”
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.
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.
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.
database system
An organization of components that defines and regulates the collection, storage, management, and use of data in a database environment.
desktop database
A single-user database that runs on a personal computer.
distributed database
A logically related database that is stored over two or
more physically independent sites.
enterprise database
The overall company data representation, which provides
support for present and expected future needs.
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.
file
A named collection of related records.
information
The result of processing raw data to reveal its meaning.
Information consists of transformed data and facilitates decision making.
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.
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.
logical data format
The way in which a human being views data.
metadata
Data about data, that is, data concerning data characteristics and
relationships. See also data dictionary.
multiuser database
A database that supports multiple concurrent users.
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.
performance tuning
Activities that make a database perform more efficiently
in terms of storage and access speed.
physical data format
The way in which a computer “sees” (stores) data.
production database
The main database designed to keep track of the day-to-
day operations of a company. See also transactional database.
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.
query language
A nonprocedural language that is used by a DBMS to manipulate its data. An example of a query language is SQL.
query result set
The collection of data rows that are returned by a query.
record
A collection of related (logically connected) fields.
single-user database
A database that supports only one user at a time.
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.
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.
transactional database
A database designed to keep track of the day-to-day transactions of an organization. See also production database.
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.
attribute
A characteristic of an entity or object. An attribute has a name and a
data type.
business rule
Narrative descriptions of a policy, procedure, or principle within
an organization. Examples: A pilot cannot be on duty for more than 10 hours during a 24-hour period. A professor may teach up to four classes during any one semester.
class
A collection of like objects with shared structure (attributes) and behavior (methods). A class encapsulates an object’s data representation and a method’s implementation. Classes are organized in a class hierarchy.
class hierarchy
The organization of classes in a hierarchical tree where each “parent” class is a superclass and each “child” class is a subclass. See also inheritance.
conceptual model
The output of the conceptual design process. The conceptual model provides a global view of an entire database. Describes the main data objects, avoiding details.
conceptual schema
A representation of the conceptual model, usually expressed graphically. See also conceptual model.
connectivity
Describes the classification of the relationship between entities. Classifications include 1:1, 1:M, and M:N.
constraint
A restriction placed on data. Constraints are normally expressed in the form of rules. Example: “A student’s GPA must be between 0.00 and 4.00.” Constraints are important because they help to ensure data integrity.
Crow’s Foot notation
A representation of the entity relationship diagram using a three-pronged symbol to represent the “many” sides of the relationship.
data definition language (DDL)
The language that allows a database administrator to define the database structure, schema, and subschema.
data management language (DML)
The language (set of commands) that allows an end user to manipulate the data in the database (SELECT, INSERT, UPDATE, DELETE, COMMIT, and ROLLBACK).
data model
A representation, usually graphic, of a complex “real-world” data structure. Data models are used in the database design phase of the database life cycle.
entity
Something about which someone wants to store data; typically a person, a place, a thing, a concept, or an event. See also attribute.
entity instance entity occurrence (see entity instance it said for definition)
A term used in ER modeling to refer to a specific table row. Also known as an entity occurrence.
entity relationship diagram (ERD)
A diagram that depicts an entity
relationship model’s entities, attributes, and relations.
entity relationship (ER) model (ERM)
A data model developed by P. Chen in
1975. It describes relationships (1:1, 1:M, and M:N) among entities at the
conceptual level with the help of ER diagrams.
entity set
In a relational model, refers to a grouping of related entities.
extended relational data model (ERDM)
Sometimes referred to as the
enhanced entity relationship model; the result of adding more semantic constructs (entity supertypes, entity subtypes, and entity clustering) to the original entity relationship (ER) model.
