Chapter 1 Database Theory
Field
A characteristic or group of characteristics (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.
Database Management System (DBMS)
Collection of programs - Manage structure and controls access to data
End-User Data
Raw facts of interest to end users
Physical Data Format
The way in which a computer "sees" information.
Logical Data Format
The way in which a human being views data.
Advantages of DBMS
-Improved data sharing. -Improved data security. -Better data integration. -Minimized data inconsistency. -Improved data access. -Improved decision making. -Increased end-user productivity.
Role of DBMS
-Intermediary between the user and the database. -Database structure stored as file collection. -Access database through the DBMS. -DBMS enables data to be shared. -DBMS integrates many users' views of the data.
Databases can be classified according to
-Number of users. -Database location(s). -Expected type and extent of use.
Ad 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 definitions 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.
Passive Data Dictionary
A DBMS data dictionary that requires an end-user-initiated command to update its data access statistic.
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.
Active Data Dictionary
A data dictionary that is automatically updated by the database management system every time the database is accessed, thereby keeping its information current.
Transactional Database
A database design to keep track of the day to day transactions of an organization.
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. Example: SQL.
Structured Query Language (SQL)
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.
Desktop Database
A single-user database that runs on a personal computer.
Island 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.
Metadata
Data about data. Provides a description of data characteristics and relationships in data. - Complements and expands value of data
Distributed Database
Data distributed across several different sites.
Centralized Database
Data located at a single site.
Unstructured Data
Data that exists in their original state.
Semistructured Data
Data that has been processed to some extent.
Organizational Survival
Good decision making is the key.
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. The foundation of information. Must be formatted for for storage, processing, and presentation.
Extensible Markup Language (XML)
Represents data elements in textual format.
Good Decision Making
Requires accurate, relevant, and timely information.
Structured Data
Results from formatting. Structure based on type of processing to be performed.
Database
Shared integrated computer structure that stores a collection of data (End-user data and Metadata)
Data Warehouse
Stores data used for tactical or strategic decisions.
Operational Database
Supports a company's day-to-day operations. Sometimes called a transactional or production database.
Multiuser Database
Supports multiple users at the same time. Example: Workgroup database and enterprise database.
Single User Database
Supports only one user at a time. Example: A desktop database.
XML Database
Supports semistructured XML data.
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.
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 meaning. The bedrock of knowledge.
