What Is a Database?

Chapter 14
Databases and Database Management Systems
What Is a Database?
Database—a collection of related data stored and organized in a manner so it can be
retrieved as needed.
Database management system (DBMS)—the software used to create, maintain,
and access computer databases.
Databases typically consist of tables containing fields (columns) and records
Individuals Involved With a Data Management System
Database designers
Database developers and programmers
Database administrators
Evolution of Databases
Advantages and Disadvantages of the Database Approach
 Better information.
 Faster response time.
 Lower operating costs and storage requirements.
 Improved data integrity and better data management.
 Higher software cost.
 Increased vulnerability .
Data Concepts and Characteristics
Data hierarchy (characters, fields/columns, records/rows, tables, database).
Entity relationships:
 One-to-one relationships
 One-to-many relationships
Many-to-many relationships
Data Concepts and Characteristics, Cont’d.
Data definition—the process of describing the characteristics of data that is to be
included in a database table.
For each field, need to define:
 Name (must be unique within the table).
 Data type (such as number, text, date, and so forth).
 Any needed properties (such as any allowable range or required format).
Data dictionary—contains all data definitions for a database (metadata).
Data integrity—the accuracy of data.
Data validation—the process of ensuring that data entered into the database
matches the specifications.
Data security—protecting data against destruction and misuse.
Data organization: most methods use a primary key.
 Indexed organization—uses an index to keep track of where each record is
 Direct organization—uses hashing procedures with a record’s primary key field
to determine the storage location.
Database Classifications
Single-user vs. multiuser systems
Client-server systems
Database Classifications
N-tier database systems (middle tiers contain one or more programs stored on one or
more computers).
Centralized vs. distributed database systems.
In-memory databases.
Database Models
Five main models:
 Hierarchical
 Network
 Relational
 Object-oriented
 Multidimensional
Relational Database Model
Relational database management system (RDBMS)
Designing a relational database:
 Identify the purpose of the database and needed output.
 Determine the tables and fields.
 Assign the fields to the appropriate tables and restructure as needed
(normalization process).
 Finalize the structure (data definition process).
Creating a relational database:
 Create the structure of the table.
 Enter data using a created form or the regular Datasheet view.
 Tables can be related.
 Tables can be modified using the Design view, if needed.
Retrieving information from a relational database
 Queries (SQL or built-in query features)
 Reports (more formal output)
Maintaining a relational database
 Modifying the table structure.
 Adding new indexes to speed up queries.
 Deleting obsolete data.
 Upgrading database software and installing patches.
Repairing or restoring data that has become corrupt.
Object-Oriented Database Model
Can contain a wide variety of objects (text, graphics, music, DNA, photographs, etc.).
Objects are manipulated with methods, similar to object-oriented programs.
Creating using an object-oriented database management system (OODBMS).
Multidimensional Databases
Typically contains data collected from enterprise-wide activities.
Can be viewed from multiple perspectives (dimensions).
Commonly used with data warehousing.
Database and the Web
Database are commonly used in conjunction with Web pages, such as for:
 Information retrieval
 E-commerce
 Dynamic Web pages
How Web Databases Work
Database use often initiated with a request from the Web page visitor.
Middleware—used to connect the Web page to the database.
 Common types of middleware:
 CGI (common gateway interface)
 API (application interface)
 PHP (PHP Hypertext Preprocessor)
Key Terms
Data definition
Data dictionary
Data integrity
Data security
Data validation
Database management system
Direct organization
Indexed organization
Multidimensional database
Object-oriented database
management system
Primary key
Relational database
management system
Structured query language