1 chapter 14 understanding computers, 11 th edition 14 databases and database management systems...

1Chapter 14 Understanding Computers, 11th Edition

14Databases and

Database Management Systems

TODAY AND TOMORROW

11th Edition

CHAPTERCHAPTER


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.


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.


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


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


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


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


The Evolution of Databases


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)


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)


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


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


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


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


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


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


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


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


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


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


The Relational Database Model, Cont’d

Properly designing a relational database before creating it is important



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



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



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


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


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


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


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


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)


Summary What Is a Database?

Data Concepts and Characteristics

Database Classifications

Database Models

Databases and the Web

1 chapter 14 understanding computers, 11 th edition 14 databases and database management systems...

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