Download Sequential Query Language - personal.kent.edu

Page |1
2007
Sequential Query Language
Database Networking Using SQL
Sequential query language (SQL) is used in combination with a SQL database
server to store and access data over large networks quickly, efficiently, and
securely. This paper aims to define SQL in simple and understandable terms in
order to relate how SQL is implemented and used in a network environment. The
scope of this paper is limited to a basic understanding of what SQL is and how it
relates to networking. For a better understanding of SQL server processes see the
reference section at the end of this paper for further study.
William Butterfield
Kent State University
9/2/2007
Page |2
Defining SQL
SQL, pronounced “sequel” or “S-Q-L” by some, is a programming language used to access data stored in
a network database such as MS SQL or MySQL. SQL is an acronym for “sequential query language”. If
you are not familiar with relational databases, SQL commands are used to generate snapshots of data
within SQL database tables by issuing queries. A query is an inquiry request by a user into a database
table in which the computer searches the particular information requested. SQL uses simple terms such
as “SELECT”, “INSERT”, or “DELETE” to access data in a database table. For example, if I had a table that
consisted of one thousand people, separated by their first and last names, I could query the table to find
all of the people with the first name of “Bob” by using the SELECT command. Conversely, I could delete
all instances of the name “Bob” by using the DELETE command. I could also insert a new “Bob Smith” by
using the INSERT command. SQL is a very popular network database language because SQL database
engines are freely available to download and are more efficient to use across medium and large size
networks than stand alone database programs such as Microsoft Access.
Example of a SQL Query Statement:
The above example shows the language of SQL used to access and display customer information from a
database object (DBO) called customers. All of the database table fields that have been requested by
the statement follow the SELECT statement. The condition, TOP 100 PERCENT, means that all of the
records found will be displayed. Lastly, this statement specifies two additional conditions to display the
data. First, customers that have a preexisting condition that they should not be listed are not shown
(i.e. WHERE (do_not_list = 0), and the list will be ordered alphabetically by customer name.
In order to run this statement, a SQL server database engine,
sometimes referred to as a SQL server or SQL database engine, is
required to run the query on the database. SQL servers are
SQL Server Instance Icon
software programs that run on a computer. Most SQL servers do
not require any special hardware requirements and can run on
virtually any computer platform. Once the SQL server software is installed and an instance of SQL server
is running on the computer, SQL statements can now be created and run to retrieve information from
the database. Above is an example of the icon displayed in the system tray of a Windows 2003 Server
running an instance of MS SQL Server 2005 Express Edition and the accompanying fly-out information
that states that the SQL services are currently ready to accept commands running on this machine.
Requirements for Using SQL
Since SQL is essentially a programming language used to access a database, several related items
become necessary to use and implement SQL. First, SQL needs a database to access. Two very
commonly used SQL database engines are MS SQL 2005 Express Edition and MySQL. Both are free to
download and provide basic functionality. The Microsoft SQL database engine provides a stripped down
version of their full blown enterprise version that provides additional reporting and logging services for
heavy duty transactional servers. The MySQL AB version is an open source and completely modifiable
version of the same database architecture, and provides an enterprise version for a sale as well.
Page |3
SQL Server 2005 Management Studio Express
Once a SQL database engine is chosen and installed, a SQL database
interface needs to be installed to set up individual databases and
tables and to secure the data from unauthorized users. Database
management software is often coupled with the database engine
download from Microsoft or MySQL AB. To the left is a screenshot
of SQL Server Management Studio Express which is an excellent
database interface and can easily be used to set up and administer
SQL databases.
Lastly, to provide a visual way for displaying the data stored in the
database, one needs to use some sort of networking platform for
displaying the data. One common solution is to use Microsoft Visual
Studio. This program assists the database developer in creating
intranet or internet sites that connect to the SQL database engine to
display the data in web browsers. Using Visual Studio will help
create the necessary web pages, but the developer will need an
additional web server component to broadcast the site across the network. An easy solution to this is to
download Apache. Apache is a free web server engine that will run on just about any platform,
however, for people with a Windows 2000 Professional, XP Professional, or Windows Server 2003
machines, Internet Information Services (IIS) is made available to use by Microsoft as part of the
operating system.
SQL Server Network Requirements
Database
Essentials
Network
Essentials
Options
•SQL Server Database Engine
•SQL Server Database Management Tool
•Examples include: MS SQL 2005 Express Edition and SQL Server Management Studio Express, both are free to download.
•Establish a database interface for users to view the data
•Using a web development tool such as Visual Web Studio is easy and free to download.
•If creating a SQL database for network use, your computer needs to be running a web service such as Apache or IIS.
•Full blown packages for free are available to dowload and install on both Windows and Linux computers
•WAMP servers: Windows, Apache, MySQL, PHP
•LAMP servers: Linux, Apache, MySQL, PHP
To make things easier for developers, there are many sites that offer a comprehensive collection of all of
these tools for free in one inclusive download. To download all of the necessary components and get up
and running a SQL server on a Windows machine or Linux machine quickly, several web sites make this
process quick and easy. Many of these types of web sites have download links for “WAMP” servers or
“LAMP” servers. A WAMP server download is a “package” designed to integrate on a Windows machine
an Apache Web Server, MySQL database engine, and PHP web server services for dynamic web page
execution. A LAMP server package will setup the components on a Linux computer. Below are two web
sites for obtaining these packages:


http://www.wampserver.com/en/download.php
http://www.devside.net/server/webdeveloper
Page |4
Everything that has been listed so far is available to download on the internet for free. There are,
however, many retail programs for sale that can assist in SQL database development and deployment
such as Adobe ColdFusion (formerly made by Macromedia), Oracle, Microsoft SQL Enterprise Edition, as
well as many others. These are often cost prohibitive for most enthusiasts or students, but do provide
much more flexibility and functionality for network database intensive development and deployment.
Database Networking
SQL server databases are often used in medium to large network situations. Stand alone databases can
be used across networks on very small networks of four to five computers in limited capacities without
many problems. However, if the data in the database is being accessed by more than five users
simultaneously it becomes increasingly necessary from a speed and database integrity standpoint to rely
on the stability and reliability of a SQL database engine. The reason why is because SQL database
engines protect data from network problems, such as data packet collisions on the network, by acting as
a traffic controller and central manager of the information. By acting as the single point of entry it keeps
the data safe from corruption by multiple requests being implemented at exactly the same time. In this
manner, requests for the data are queued and implemented one at a time. A SQL server timestamps
each transaction that occurs in the database table in case a major problem arises or if a conflict takes
place and it needs to decide what to do. For example, if two users access the same record at the same
time, and each save different information to that record, SQL will choose a “winner” and a “loser” for
that particular record. Only the winner’s data will be written to the master database table and an error
message will be sent to the “loser” indicating that their record was not saved to the database table.
Across large networks of hundreds and even thousands of people accessing a database, this can be
extremely helpful in making sure that database tables do not get corrupted or that information does not
get accidentally changed.
SQL servers are often confused by the uninformed as large machines that only large corporations can
afford to buy. This is far from the truth. SQL server software can be installed and run on virtually any
computer today and can be helpful to create, access, and organize information with the flexibility of
collecting the simplest of data to complex multidimensional tables of related information. If you are not
experienced with relational databases, I suggest looking into Microsoft Access. Additionally, an
excellent learning manual to accompany your learning process is the Access 2007 Bible, by Groh,
Stockman, Powell, Prague, Irwin, and Reardon. In my opinion, the Access 2002 Bible covers SQL
database implementation in greater depth than the 2007 republication, but may be harder to find than
the 2007 release. If you have used dynamic (interactive) web sites in the past, most likely they are
driven by accessing backend SQL server databases. Within the professional world, many groups
including businesses, educational institutions, and government agencies are turning toward intranet
sites that collect information in SQL databases to share, collect, and update information in real time.
SQL allows us to efficiently and securely provide network users the ability to interact with information in
more meaningful ways than the static displays of database tables. As the internet continues to become
more dynamic and interactive, the use of SQL server databases will become increasingly popular to use
and connect network users to the information requested by web site visitors.
Page |5
References
1. Cary N. Prague and Michael R. Irwin. Access 2002 Bible. Indianapolis, Indiana: Wiley
Publishing, 2001.
2. Julie C. Meloni. Sams Teach Yourself PHP, MySQL, and Apache. Indianapolis, Indiana: Sams
Publishing, 2004.
3. Michael R. Groh, Joseph C. Stockman, Gavin Powell, Cary N. Prague, Michael R. Irwin, and
Jennifer Reardon. Access 2007 Bible. Indianapolis, Indiana: Wiley Publishing, 2007.
4. Mike Gunderloy and Susan Harkins. Mastering SQL Server 2005 Express Edition. Indianapolis,
Indiana: Wiley Publishing, 2006.