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1Chapter 14 Understanding Computers, 11th Edition
14Databases and
Database Management Systems
TODAY AND TOMORROW
11th Edition
CHAPTERCHAPTER
2Chapter 14 Understanding Computers, 11th Edition
Learning Objectives Explain what a database is, including common
database terminology, and list some of the advantages and disadvantages of using databases.
Discuss some basic concepts and characteristics of data, such as data hierarchy, entity relationships, data definition, and organization.
Describe the importance of data integrity, security, and privacy and how it affects database design.
3Chapter 14 Understanding Computers, 11th Edition
Learning Objectives, Cont’d Identify some basic database classifications and
discuss their differences.
List the most common database models and discuss how they are used today.
Understand how a relational database is designed, created, used, and maintained.
Describe some ways databases are used on the Web.
4Chapter 14 Understanding Computers, 11th Edition
Overview This chapter covers:
What databases are and advantages for using them
Database concepts and vocabulary
Key characteristics about the data in a database
Database classifications and models
The relational database model
How databases are used on the Web
5Chapter 14 Understanding Computers, 11th Edition
What Is a Database? 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
6Chapter 14 Understanding Computers, 11th Edition
Relational Databases: A Simple Example
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
7Chapter 14 Understanding Computers, 11th Edition
8Chapter 14 Understanding Computers, 11th Edition
Individuals Involved With a Database Management System
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
9Chapter 14 Understanding Computers, 11th Edition
The Evolution of Databases
10Chapter 14 Understanding Computers, 11th Edition
Advantages and Disadvantages of the Database Approach
Advantages
Better information
Faster response time
Lower operating costs and storage requirements
Improved data integrity and better data management
Disadvantages
Higher software cost
Increased vulnerability (backup is essential)
11Chapter 14 Understanding Computers, 11th Edition
Data Concepts and Characteristics Data in a database has a certain hierarchy
Characters
Fields/columns (hold single pieces of data)
Records/rows (groups of related fields)
Tables (collection of related records)
Database (contains a group of related tables)
12Chapter 14 Understanding Computers, 11th Edition
Data Concepts and Characteristics, Cont’d
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
13Chapter 14 Understanding Computers, 11th Edition
Data Concepts and Characteristics, Cont’d
Data definition: process of describing the characteristics of data that is to be included in a database table
During data definition, each field is assigned: Name (must be unique within the table) Data type (such as Text, Number, Currency, or
Date) Properties (field size, format of the field, allowable
range, input mask, etc.) Finished specifications for a table become the table
structure
14Chapter 14 Understanding Computers, 11th Edition
15Chapter 14 Understanding Computers, 11th Edition
Data Dictionary 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
16Chapter 14 Understanding Computers, 11th Edition
Data Integrity, Security, and Privacy 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
17Chapter 14 Understanding Computers, 11th Edition
18Chapter 14 Understanding Computers, 11th Edition
Data Integrity, Security, and Privacy, Cont’d
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
19Chapter 14 Understanding Computers, 11th Edition
Data Organization 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
Direct organization: uses hashing to specify the exact storage location
20Chapter 14 Understanding Computers, 11th Edition
21Chapter 14 Understanding Computers, 11th Edition
Database Classifications 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
22Chapter 14 Understanding Computers, 11th Edition
Database Classifications, Cont’d 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
23Chapter 14 Understanding Computers, 11th Edition
24Chapter 14 Understanding Computers, 11th Edition
Database Models Two older models are:
Hierarchical databases: store data in the form of a tree, with typically a one-to-many relationship between data entities
Network databases: the relationship between data elements is usually either one-to-many or many-to-many
25Chapter 14 Understanding Computers, 11th Edition
26Chapter 14 Understanding Computers, 11th Edition
The Relational Database Model Relational database management system
(RDBMS): data is stored in tables related by common fields; the most widely used database model today
27Chapter 14 Understanding Computers, 11th Edition
The Relational Database Model, Cont’d
Properly designing a relational database before creating it is important
28Chapter 14 Understanding Computers, 11th Edition
The Relational Database Model, Cont’d
To create a relational database:
Create the structure of each individual table
Enter data using a created form or the regular Datasheet view
Migrate any existing data to the new database
Modify tables, if needed, using the Design view
Relate tables as needed
29Chapter 14 Understanding Computers, 11th Edition
30Chapter 14 Understanding Computers, 11th Edition
31Chapter 14 Understanding Computers, 11th Edition
32Chapter 14 Understanding Computers, 11th Edition
The Relational Database Model, Cont’d
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
33Chapter 14 Understanding Computers, 11th Edition
34Chapter 14 Understanding Computers, 11th Edition
The Relational Database Model, Cont’d
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
35Chapter 14 Understanding Computers, 11th Edition
36Chapter 14 Understanding Computers, 11th Edition
Relational Database Model, Cont’d Relational databases typically require ongoing
maintenance, including:
Modifying the table structure when needed
Adding new indexes to speed up queries
Deleting obsolete data
Upgrading database software, installing patches
Repairing/restoring data that has become corrupt
Continuing to evaluate and improve security
37Chapter 14 Understanding Computers, 11th Edition
The Object-Oriented Database Model 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 object-oriented 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
38Chapter 14 Understanding Computers, 11th Edition
39Chapter 14 Understanding Computers, 11th Edition
Multidimensional Databases 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
40Chapter 14 Understanding Computers, 11th Edition
Databases and the Web Databases are commonly used on the Web, such as
for: Information retrieval Dynamic Web pages (change based on user
input) E-
commerce
41Chapter 14 Understanding Computers, 11th Edition
Databases and the Web, Cont’d 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)
42Chapter 14 Understanding Computers, 11th Edition
43Chapter 14 Understanding Computers, 11th Edition
Summary What Is a Database?
Data Concepts and Characteristics
Database Classifications
Database Models
Databases and the Web