Transcript Understanding Computers, 11/e, Chapter 14

11th Edition
TODAY AND TOMORROW
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CHAPTER
Chapter 14
Databases and
Database
Management Systems
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Learning Objectives
Chapter 14
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Explain what a database is, including common
database terminology, and list some of the
advantages and disadvantages of using databases.
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Discuss some basic concepts and characteristics of
data, such as data hierarchy, entity relationships,
data definition, and organization.
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Describe the importance of data integrity, security,
and privacy and how it affects database design.
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Learning Objectives, Cont’d
Chapter 14
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Identify some basic database classifications and
discuss their differences.
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List the most common database models and discuss
how they are used today.
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Understand how a relational database is designed,
created, used, and maintained.
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Describe some ways databases are used on the
Web.
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Overview
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This chapter covers:
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What databases are and advantages for using
them
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Database concepts and vocabulary
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Key characteristics about the data in a database
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Database classifications and models
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The relational database model
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How databases are used on the Web
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What Is a Database?
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Database: a collection of related data stored in a
manner so it can be retrieved as needed
Database management system (DBMS): used to
create, maintain, and access computer databases
A database typically consists of:
 Tables: in a relational database, a collection of
related records
 Fields (columns): single category of data to be
stored in a database
 Records (rows): collection of related fields in a
database
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Relational Databases: A Simple
Example
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In a relational database, data from several tables is
tied together (related ) using a field that the tables
have in common
Primary key: specific field in a database table that
uniquely identifies the records in that table
DBMSs available for use on PCs include
 Microsoft Access (most widely used)
 Corel Paradox
 Lotus Approach
For more comprehensive enterprise databases
 Oracle
 IBM DB2
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Individuals Involved With a Database
Management System
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Users: use an interface to enter data, update data,
and pull information out of the database
Database designers: design the database
Database developers: create the database
Database programmers: write the programs needed
to access the database or tie the database to other
programs
Database administrators: responsible for managing
the large databases found within an organization
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The Evolution of Databases
Chapter 14
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Advantages and Disadvantages of
the Database Approach
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Advantages
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Better information
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Faster response time
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Lower operating costs and storage requirements
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Improved data integrity and better data
management
Disadvantages
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Higher software cost
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Increased vulnerability (backup is essential)
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Data Concepts and Characteristics
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Data in a database has a certain hierarchy
 Characters
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Fields/columns (hold single pieces of data)
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Records/rows (groups of related fields)
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Tables (collection of related records)
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Database (contains a group of related tables)
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Data Concepts and Characteristics,
Cont’d
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Entity: something of importance to the organization
 Entities that the organization wants to store data
about typically becomes a database table
Relationships
Attributes: characteristics of entities
 Attributes typically become fields in the entity’s
database table
Entity relationships
 One-to-one (1:1) entity relationships
 One-to-many (O:M) entity relationships
 Many-to-many (M:M) entity relationships
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Data Concepts and Characteristics,
Cont’d
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Data definition: process of describing the
characteristics of data that is to be included in a
database table
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During data definition, each field is assigned:
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Name (must be unique within the table)
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Data type (such as Text, Number, Currency, or
Date)
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Properties (field size, format of the field, allowable
range, input mask, etc.)
Finished specifications for a table become the table
structure
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Data Dictionary
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Data dictionary: repository of all data definitions in a
database
 Includes data about the data in the tables
(metadata), such as:
 Table structures
 Security information (passwords, etc.)
 Relationships between the tables in the database
 Current information about each table, such as the
current number of records
 Ensures that data being entered into the database
does not violate any specified criteria
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Data Integrity, Security, and Privacy
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Data integrity: the accuracy of data
 Quality of data input determines the quality of
retrieved information (GIGO)
Data validation: ensuring that data entered into the
database matches the data definition
 Helps to increase data integrity
 Can be enforced on a per transaction basis so the
entire transaction will fail if one part is invalid
Database locking: prevents two individuals from
changing the same data at the same time
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Data Integrity, Security, and Privacy,
Cont’d
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Data security: protecting data against destruction
and misuse
 Prevents access from unauthorized individuals
 Protects against data loss
 Protects against both intentional and unintentional
problems
 Should include strict backup and disaster-recovery
procedures (disaster-recovery plan)
Data privacy: growing concern because of the vast
amounts of personal data stored in databases today
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Data Organization
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Data organization: arranging data for efficient
retrieval
 Indexed organization: uses an index to keep
track of where data is stored
 Index: small table containing a primary key and
the location of the record belonging to that key
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Direct organization: uses hashing to specify the
exact storage location
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Database Classifications
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Single-user database systems: designed to be
accessed by one user
Multiuser database systems: designed to be
accessed by multiple users (most business
databases today)
Client-server
database
systems: has
both clients and
at least one
server
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Database Classifications, Cont’d
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N-tier database systems: have more than two tiers
 Middle tiers contain one or more programs stored on
one or more computers
Centralized database systems: Database is located on
a single computer, such as a server or mainframe
Distributed database systems: Data is physically divided
among several computers connected by a network, but
the database logically looks like it is a single database
In-memory databases (IMDBs): Data is stored in main
memory, instead of on disk
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Database Models
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Two older models are:
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Hierarchical databases: store data in the form of a
tree, with typically a one-to-many relationship
between data entities
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Network databases: the relationship between data
elements is usually either one-to-many or manyto-many
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The Relational Database Model
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Relational database management system
(RDBMS): data is stored in tables related by
common fields; the most widely used database
model
today
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The Relational Database Model,
Cont’d
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Properly designing a relational database before
creating it is important
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The Relational Database Model,
Cont’d
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To create a relational database:
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Create the structure of each individual table
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Enter data using a created form or the regular
Datasheet view
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Migrate any existing data to the new database
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Modify tables, if needed, using the Design view
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Relate tables as needed
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The Relational Database Model,
Cont’d
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To retrieve information from a relational database,
can use a:
 Query: a request to see information from a
database that matches specific criteria
 Often written in structured query language
(SQL)
 Many programs have wizards or other tools to
make it easy to create a query
 Can specify the fields to be displayed
 Specify which records should be retrieved by
specifying criteria
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Chapter 14
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The Relational Database Model,
Cont’d
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To retrieve information from a relational database, can
use a:
 Report: formatted means of looking at a database
table or the results of a query
 Reports can pull data from more than one table
 Includes headings, formatting, etc.
 Many programs have wizards or other tools to
make it easy to create a report
 Both reports and queries are saved so they can
be retrieved again when needed
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Relational Database Model, Cont’d
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Relational databases typically require ongoing
maintenance, including:
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Modifying the table structure when needed
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Adding new indexes to speed up queries
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Deleting obsolete data
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Upgrading database software, installing patches
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Repairing/restoring data that has become corrupt
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Continuing to evaluate and improve security
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The Object-Oriented Database Model
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Object-oriented database management system
(OODBMS): a type of database system in which
multiple types of data are stored as objects along with
their related code
Objects consist of related attributes stored with
methods associated with the object, similar to objectoriented programs
Objects in an OODBMS can contain virtually any type
of data—video clip, photograph with a narrative, text
with music, and so on—along with its related code
Object-relational database management systems
(ORDBMS) also exist
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Chapter 14
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Multidimensional Databases
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Multidimensional database (MDDB): a type of
database in which data can be viewed from multiple
dimensions or perspectives
 Commonly used with data warehousing
 Often used in conjunction with: Online Analytical
Processing (OLAP)
 MOLAP (Multidimensional OLAP): data stored in
single structures called data cubes
 ROLAP (Relational OLAP): information stored in
an existing relational database using tables to
store the summary information
 HOLAP (Hybrid OLAP): combination of MOLAP
and ROLAP technologies
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Databases and the Web
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Databases are commonly used on the Web, such as
for:
 Information retrieval
 Dynamic Web pages (change based on user
input)
 Ecommerce
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Databases and the Web, Cont’d
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Requests to retrieve or store information from or in a
Web database is typically initiated by the Web site
visitor
Web server converts the request into a database
query and passes it onto the database server, and
then sends the results back to the visitor
Middleware is used to connect two otherwise
separate applications, such as a Web server and a
database management system
 CGI (common gateway interface)
 API (application interface)
 PHP (PHP Hypertext Preprocessor)
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Chapter 14
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Summary
Chapter 14
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What Is a Database?
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Data Concepts and Characteristics
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Database Classifications
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Database Models
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Databases and the Web
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