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Intranets
Chapter 28
Using Web-to-Database Query Tools
CONTENTS
The most important information on an intranet typically is housed
in databases. These databases can be on a single site, although
typically, they can be found all across an entire intranet.
Most of these databases have been around since long before the
Internet became popular, and before any corporate intranets were
built. That means that they've been built without TCP/IP in mind,
without HTML in mind, and without taking into account any other
intranet technologies. Before the intranet was built, they were
accessed in a variety of ways, depending on the particular kind
of database and access software used.
An intranet can theoretically make it much easier to get at all
that corporate data. The use of HTML means that it's relatively
easy to build search forms that anyone can use to easily get at
data-data that in order to get at, people previously may have
been required to know a database programming language.
However, while it's easy to build HTML search forms that let people
type in queries, it's not so easy to actually have those queries
be sent out to search through a database, and then to have the
results be delivered back to whoever did the searching.
That's what Web-to-database query tools are designed to do. They're
designed to let anyone, without having to understand database
languages, easily get at the vast corporate resources locked up
in databases.
Since the databases typically were built before the intranet,
some means of getting at them from an intranet, and specifically
from the Web, needs to be designed. There are many different ways
of accessing corporate databases from an intranet. A popular one
is to use the Common Gateway Interface (CGI). CGI enables people
on the Web to access resources that aren't directly located on
the Web. Through the use of CGI scripts, an intranet programmer
can allow someone from the Web to query a database, and have that
database send back information that is put into a preformatted
HTML page. This makes it easy for anyone, using a standard Web
browser such as Netscape Navigator or Internet Explorer, to access
corporate databases.
What will undoubtedly prove to be popular is the Structured Query
Language (SQL). SQL is a database language that works on a client/server
model, as does much of the Web. In the SQL model, the database
itself is separate from the software that accesses the data-in
other words, the software used to access the database is the client,
while the database itself is the server. There can be many different
kinds of clients to access the same underlying database. One such
client can be a CGI script that takes the input form on the corporate
Web, converts its contents into an SQL query, and submits it to
the database server. Another client could be a Java applet that
allows for the creation of more complex queries and better data
display than standard HTML.
The most important information on most intranets exists on databases
that were created long before the Internet became popular, and
before intranets were ever created. They use technology built
without the TCP/IP protocols or the HTML language in mind. However,
there needs to be some way for people on an intranet to access
and use that data. A variety of techniques have been developed
for doing this that involve allowing people to search the databases
from within a Web browser.
- When someone on an intranet wants to gain access to a corporate
database, he or she will typically use a Web browser and visit
a particular home page. This home page sits on a Web server that
essentially acts as a front end to the database. The database
in fact sits on another computer on the intranet, not the Web
server.
- When someone wants to search a database, they use a form built
with HTML. After they type in search terms, the search terms are
sent using a Common Gateway Interface (CGI) script. CGI is a method
that enables databases and other resources to be accessed from
the Web. CGI scripts can be written with a number of different
tools and programming languages, including UNIX's Perl, or the
C programming language.
- The CGI script is programmed to take the information entered
on the Web form and translate it into a properly formed SQL query
the database server can process.
- The CGI script now acts as a client to the database server.
It makes a connection to the database and submits the SQL query
it created. To the database server it appears to be just another
client connecting rather than a connection via a Web browser.
- The database performs the requested query and sends the matching
records back to the CGI script. These results are properly reformatted
through the addition of HTML tags.
- The formatted information from the database is sent back to
the browser that requested it. The user can now use that HTML
page like any other HTML page.
Contact
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Copyright 1998 Macmillan Computer Publishing. All rights reserved.
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