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T4L1
Databases
Introduction
This lesson is designed to expose you to the concept of database technology and it’s use
on the Internet today. By the end of this lesson you should be able to:
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Define what a database is.
Define what a database management system is.
Recognize the difference between an enterprise database management system and
a personal database management system.
Define what SQL is.
Define benefits of using a database with your web site.
Define what a static web site is.
Define what a dynamic web site is.
The concept of databases has been around for quite some time. With the advent of the
web, it is a natural progression for the database to extend itself from the client-server
model to a web-enabled model. Web sites have been using databases to produce their
content for a number of years.
Databases
 Database Definition
 Database Management System Definition
 Personal DBMS
 Enterprise DBMS
 Databases and SQL
Web Enabled Databases
 Benefits of Using a Database
 Static Web Sites
 Dynamic Web Sites
 Trends in DBMS for the Web
Additional Resources
CNET Builder.com
[[ link to http://www.builder.com/Programming/Databases/ ]]
ahref.com
[[ link to http://www.ahref.com/guides/technology/199806/0622piou.html ]]
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Web Developers Virtual Library
[[ link to http://www.wdvl.com/Authoring/DB/Intro/ ]]
Database Definition
A Database Defined
A database stores information in a planned format for future retrieval. This section will
explain the basic concepts and terminology behind most databases.
File
[[these graphics were created by Brett Bixler. IST has permission to use them if they
want.]]
A database file is a collection of related information. Each file stores information about
one topic.
Record
A database consists of one or more records of information. Each record is a collection of
information about one person, place, or thing. A record contains all the pieces of
information about a particular subject. For example, if you had a database of people you
correspond with, each record would contain information on one person. If your database
contained 20 records, you would have information on 20 people.
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Field
Each record in a database contains different pieces of information called fields. A field is
one item contained in the record. It is one component of the record.
In the example of a database of people you correspond with, each record might have a
name field, an address field, and a telephone number field.
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Field Types
Fields can hold different types of information. The most common types are listed below.
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TEXT (or character): may contain any character.
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NUMERIC: A numeric field can legally contain ONLY contain a number and
may be used in calculations.
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DATE: a user may choose different data formats to suit specific information
needs. A date may be used in day/date calculations.
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LOGICAL (sometimes called Boolean): can have one of two values. For example,
true or false. Another example is a Yes or No question.
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OTHER types: picture for graphics, calculation for mathematical manipulation of
one or more other fields in the same record, and summary for mathematical
manipulation of fields from different records, portal to link to other databases.
Databases contain large groupings of records or data such as product information, sales
transactions, statistics, multimedia, and customer profiles. Once data is in a relational or
object-oriented database one can do just about anything one wants with it.
Examples of databases encountered in everyday life include:
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TV listings
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sports statistics
airline reservation information systems
census information
real estate listings
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Database Management System Definition
A Database Management System (DBMS) is a complex software tool that allows you to
store, manage, retrieve and organize your data. This tool allow one to organize and store
this data in a way that allows us to easily update it, delete it or retrieve it. Many types of
DBMS software exist. They range from personal database software such as Microsoft
Access or Borland’s Intrabuilder to enterprise software packages such as Oracle, IBM’s
DB2, and Informix.
Initially Database Management Systems were designed for large corporations also known
as the enterprise. These corporations had the requirement to hold millions of records and
have a large number of users access this data concurrently. Additionally, these systems
had to be powerful enough to perform complex queries on the data. This traditionally
meant that only a very expensive, high-speed computer can do the job without running
into problems. Enterprise DBMS software is adept at handling these jobs but come with a
high price tag.
Additional Resources
Oracle
[[link to http://www.oracle.com ]]
IBM – DB2 websphere
[[link to http://www-4.ibm.com/software/webservers/ ]]
Informix
[[ link to http://www.informix.com/ ]]
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Personal DBMS
With the advent of cheaper and more powerful computing power, software has been
designed to closely mimic these enterprise DBMSs capabilities. The term “personal
database” software refers to a software package that can be installed on a personal
computer and require little storage space to accomplish it’s tasks.
The latest versions of personal database software do not require a database administrator
to oversee it’s proper functioning. A powerful personal database package allows for the
following:
 Scripting
 Storage of procedures
 Creation of a graphical user interface
 Reporting capabilities
Personal database software does have several drawbacks. One of them being they still do
not support a large number of concurrent users. Essentially, this means if you have a
database on an intranet or the Internet and you have many users accessing your database,
it may become corrupted and crash.
Before utilizing a database of this nature in a large environment, a proper requirements
analysis should be performed in order to determine the number of users you expect to be
using the database at any given time.
Additional Resources
Three Easy Desktop Databases for the Web
[[ link to http://www.builder.com/Programming/WebDatabases/ ]]
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Enterprise DBMS
The “enterprise” has become to be known as the collection of computers that support the
business functions of a large organization. The enterprise DBMS is complex database
software package installed and operating from a centrally located server that supports the
data needs of this enterprise. In certain network configurations, this server often ties into
several computers utilizing large storage devices such as RAID (Redundant Array of
Independent Disks) devices. Spanning the data across multiple storage devices in
multiple locations is done to improve performance and availability of data. Additionally,
this is done in order to avoid having an environmental or man-made catastrophe destroy
the data. Today’s “e” businesses are “data centric” which means they rely a great deal
upon their organizational data. Denial of accessing this data can negatively impact a
business relying on this system.
To ensure this performance is not degraded is the responsibility of a Database
Administrator (DBA). This individual is responsible for a variety of corporate critical
functions with database availability and survivability being the top two. At any given
time a DBA must be able to access the network and restore database activity to an
acceptable level. Traditionally, small and medium sized business rarely can afford to
keep on staff a DBA professional. In order to alleviate this cost, they often outsource this
function to a company that can provide the same level of service but at a lesser cost. This
is a major issue to contend with when determining your database solution.
Additional Resources:
Data Survivability White Paper
[[link to http://sdcd.gsfc.nasa.gov/ESDCD/whitepaper.data_survive.html ]]
RAID Devices
[[link to http://www.computerworld.com/home/print.nsf/all/000529E366 ]]
Disaster Recovery
[[ link to http://www.computerworld.com/home/features.nsf/all/980907disaslinks ]]
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Databases and SQL
The wide varieties of DBMSs today are relational databases that use the SQL for creating
database queries. Structured Query Language (SQL) is a relatively simple language that
you can use to access most relational databases. Even though many vendors have
developed their own variations of SQL, most of the language is standard regardless of
what DBMS you use such as Oracle, Sybase, Informix, Microsoft SQL Server, or MS
Access. IBM released the first commercial version of SQL in the early 1980s, and almost
every relational database vendor has adopted it since then.
A relational database system stores information within tables. These table structures are
comprised of rows and intersecting columns of data and are related to one another. These
columns are typically called fields. An example of a database table would be one that
would hold customer information. You can possibly have fields in your table labeled
“name”, “address”, “phone number” etc. All these fields would be related customer
information.
Using various SQL commands you are able to retrieve the data you are targeting. SQL
commands can range in complexity. Below are some examples of data being selected
from a relational database:
SELECT
customer_name
FROM
Customer
This particular SQL query would retrieve all the customer names from a relational
database table called “Customer” and display them as a list of names. Using additional
SQL command words you can make your queries return data in various formats in a
certain order and even calculated.
Additional Resources
SQL Sites
[[link to http://directory.netscape.com/Computers/Software/Databases/SQL ]]
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Benefits of Using a Database
As stated earlier in this module, relational database technologies have been around for
quite some time. The client server model, where a central database (server) serves out
data to clients (PCs), is a reliable architecture, which was a natural candidate for evolving
to the internet. Once data is stored in a database that content is ready to be conveyed
across any medium whether it be a corporate intranet, World Wide Web or even the
wireless devices available today such as PDAs and digital cell phones.
However, benefits do exist when we use a database maintain our data. First, once we
have data stored in our database it stands separate from the presentation. This allows the
various teams responsible for gathering data to not have to worry about how all the data
being collected is going to be conveyed. Secondly, and probably the most significant, is
reusability. Once your data is stored in a database you can retrieve it time and time again.
This is the primary reason we use dynamically driven web pages. Last is the ability to
update the information. Once centrally stored, we can update that information with
relative ease and all other sources pulling data from our database receive the updates.
Database technology has been getting more reliable and robust through the years.
Security features can be put into place to ensure data integrity. When these types of
features along with solid network security are put into place it also makes it difficult for
hackers or crackers to pry into your data.
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Static Web Sites
During the late 1980’s and early 1990’s the internet was made up of a large number of
web sites that were “static” in nature. These were “static” because they were primarily
created using HTML or similar markup language code. These “static” web sites had to be
updated manually any time the content changed.
Aside from animated GIFs or JAVA applets displaying some form of interactivity or
animation, these pages did not convey dynamic content. Static web sites are often
difficult to maintain, especially if you have content that changes on a regular basis. For
example, you may be required to manage a web site for a local sports team. On this site
you may have statistics on each of the players. These statistics may also appear on several
of the web pages. So each time the team plays, the statistics will change. This will require
you to change each page.
Managing a “static” site has the benefit of not requiring knowledge about databases or the
cost associated with having an Internet Service Provider (ISP) that supports database
technology. But it becomes a timely chore of making simple updates and may create the
chance for error when updating multiple pages with the same information.
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Dynamic Web Sites
From the mid to late 1990’s to today, the number database driven web sites, also known
as “dynamic” web sites have been increasing dramatically. This is primarily due to the
ease of utilizing this technology through more stable software.
“Dynamic” web sites are not just sites created using Dynamic HTML (DHTML). They
are sites that pull their content from databases and convey this content wrapped within
one of the primary markup languages available today such as HTML or XML or
programming language such as JAVA. When a visitor comes to your web site the URL
they are accessing is basically a “call” or request that goes through the web server to the
database. The database retrieves the appropriate data and returns it on the web page. Any
information stored in the database becomes a candidate for being viewed on a web page.
The benefit being all information that is updated, deleted and inserted can cascade
throughout the web site wherever it is being used.
These sites have gained in popularity now that a larger number of users are on the web
today and demand current information as know as “real time”. News sites such as
USAToday [[link to http://www.usatoday.com/]]and ESPN [[link to http://www/espn.com]], or
portals such as Excite [[link to http://www.excite.com/]] and Yahoo [[link to
http://www.yahoo.com/]] utilize database technology since visitors use them for up to the
minute (or pretty close) information.
These sites are using software such as Oracle’s WebDB or Oracle Application Server,
IBM’s Websphere, or Microsoft’s Active Server Pages (ASP). However, these software
packages require familiarity with programming and an understanding of how databases
interact with a web server. This raises the complexity of managing a web site and often
requires professionals with various technical backgrounds to make it all work.
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Trends In DBMS for the Web
Due to the value of these “dynamically” driven web sites developers now have access to
various tools that are making it possible to create database driven web sites. However,
these tools are often designed to fit certain requirements and almost always require some
sort of “tailoring.”
There are software packages available that alleviate the developer of having to know indepth programming, such as Macromedia’s Drumbeat and Allaire’s Cold Fusion.
Additionally MS Access 2000 now offers the ability to directly publish database reports
to a web server utilizing the new, interactive Data Access Pages. All of these software
packages allow you to retrieve data from personal databases or enterprise databases.
Before utilizing any of these packages it is important to determine what are the server
side requirements for each of them. Certain software packages interact better when all the
components are uniform. For example, at times Microsoft products require a complete
Microsoft solution. When a developer uses NT, SQL Server, and Microsoft Internet
Explorer to provide a web-based solution, the results tend to be more stable than if you
were running SQL server on Unix or using Netscape Server components using Internet
Explorer.
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Databases Summary
This lesson is designed for you to gain some basic information about databases and their
role with the internet. When you are finished with the lesson, you should be able to do the
following:







Define what a database is.
Define what a database management system is.
Recognize the difference between an enterprise database management system and
a personal database management system.
Define what SQL is.
Define benefits of using a database with your web site.
Define what a static web site is.
Define what a dynamic web site is.
A short summary of these topics is listed below. If you do not understand these things,
you should review the lesson at least once. If you are still having difficulty, you should
consider other sources of information that compliment this lesson, such as textbooks,
tutors, and instructors.
Database Definition
A database is an integrated collection data. When we store data in a related form using
tables this is typically a relational database.
Database Management System Definition
In order to efficiently create, store, manage and maintain a relational database, database
management systems (DBMSs) are used. These are complex software systems available
on the enterprise level and personal PC level.
Personal DBMS
The term “personal database” software refers to a database software package that can be
installed on a personal computer and require little storage space to accomplish it’s tasks.
Enterprise DBMS
The “enterprise” has become to be known as the collection of computers that support the
business functions of a large organization. The enterprise DBMS is complex database
software package installed and operating from a centrally located server that supports the
data needs of this enterprise.
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Databases and SQL
Structured Query Language (SQL) is a relatively simple language that you can use to
access most relational databases.
Benefits of Using a Database



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Data stored in a database is separate from the presentation.
Reusability.
Easy updating of information.
Ability to add security to ensure data integrity.
Static Web Sites
“Static” web sites are primarily created using HTML or similar markup language code.
They must be updated manually any time the content changes.
Dynamic Web Sites
Dynamic web sites contain web pages that are generated upon demand from a database.
Trends in DBMS for the Web
New tools are appearing that make it easier to integrate a DBMS with the delivery of web
pages. There are software packages available that alleviate the developer of having to
know in-depth programming, such as Macromedia’s Drumbeat and Allaire’s Cold
Fusion.
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