Remember I said that there are three strengths to BASIC, and I only
mentioned two. Well, here’s the last and a very important one. Within the
last couple of years a language has beendeveloped known as Visual Basic
Script, or VBScript that can run programs through web browsers such as
Netscape, Opera, and Microsoft Internet Explorer. This makes it easy to
transport some programs developed in Visual Basic to the web and
vice-versa. Not all features are supported in VBScript. For instance the
ability to read and write files through the web browser is extremely
limited so that violations of security, viruses are more difficult to
program and are not as frequent. Database programs, however, are easy to
transport and benefit the most in conversions. This allows for data in a
database is now accessible worldwide instead of companywide.
How do I do it?
VBScript is readable by web browsers as ASP (Active Server Page) files
on a Microsoft Internet Information Server (version 3.0 and later of
course). Instead of index.html we now have index.asp. The languages that
we must be familiar with also now change. We must still be familiar with
Visual Basic (ok, actually VBScript) and SQL, however, we just added HTML
(Hyper Text Markup Language). Note: HTML is a fairly simple language to
learn. If you would like more information, there are many good primers on
the web.
In Visual Basic we have forms, now our forms in a small sense become
web pages written in HTML. The way it works is that the scripts are
executed and it sends the information to the web browser in HTML form.
None of the scripting language source is viewable when it is sent, only
the HTML. For instance, here is an extremely short ASP program that will
demonstrate the HTML output.
<%@ LANGUAGE="VBScript" %>
<%
Option Explicit
Dim i
For i= 1 to
5
%> <font size=<%=i%>>Hello</font>
<%
Next
%>
When run in your web browser this output will result:
Hello Hello Hello Hello Hello
If you choose to view the source the code looks like this:
The code at the beginning: <%@ LANGUAGE="VBScript" %> denotes
that the language that will be used within this ASP is Visual Basic
Script. This line must be the first line of the code. The script part of
this page is contained within the <% %> brackets. The HTML is the
rest of the surrounding code. The value of the variable i is printed in
HTML by using the <%=i%> command. It is important to note that in
Visual Basic Script all variables are variants. This means that no
variable can be defined as a integer, string, etc.
Bring on the Databases
Like I said
before one of the greatest functions of Visual Basic is its ability to
work with databases. VBScript is also very easy to set up to access and
perform database operations. Once again we begin by setting up the
variables and connection to the database.
<%@ LANGUAGE="VBScript" %>
<%
Option Explicit
Dim Connection
Dim RS
Dim SQLStmt
Dim SSN, Firstname, Lastname
Set Connection = Server.CreateObject("ADODB.Connection")
Connection.Open "DSN=Students; UID=sa"
The Connection variable is set to the ADO (Access Data Object)
Connection type object. Once that has been set we can open the connection
through the same DSN that we set up earlier. There is no need to duplicate
the ODBC data source. Now we can set up our SQL query exactly the same way
it would appear in Visual Basic. This query will select all in the
information contained in the social security number, first name, and last
name fields in the database and then order it in alphabetical order by
lastname.
We then set the variable RS to execute this SQL Query which is
similar to the OpenRecordset function of Visual Basic.
Set RS = Connection.Execute(SQLStmt)<br>
%>
Following this we have the written the page in normal HTML. This
simply sets up the look of the beginning of the page before the data is
sent from the database.
<html>
<title>Administration Student Update</title>
<BODY BGCOLOR="FFFFFF">
<hr>
<font face="arial" size=2>
<h1>Student Information</h1>
<h2>Here are the students in the Database.
Click a name to update the student information:</h2>
We then set up a Do/While loop to go through all the records in
the database until EOF or the last record has been reached. This is
accomplished by using the RS variable with the .Fields reference. The
records are moved through by utilizing the .MoveNext function.
<%Do While
Not RS.EOF%> Name:<ahref="details1.asp?SSN=<%= RS.Fields("SSN") %>"> <b><%= RS.Fields("Lastname")%>, <%= RS.Fields("Firstname") %></b></a>
<% RS.MoveNext
Loop
%>
We then finish the page with normal HTML and we close the
connection.
<hr>
</body>
</html>
<% Connection.Close %>
In a few lines of code we have written a program to pull data from a
SQL Server database. One thing you may have noticed is the ? after the
hypertext link to the file details1.asp. This sets up a query string
within the link. A query string sends data through the URL location
(basically the address of the page) to the next page that can interpret
this information. In this case the string that is sent becomes SSN=A
Social Security Number in the database. Example: SSN=123456789. By taking
a look at details1.asp we can see how the information is used.
The value of the variable of SSN in the query string was passed onto
this page and then placed in the new Visual Basic script variable SSN by
the function Request.QueryString. It was then processed in a SQL Query and
more information on the record was extracted from the database.
By using query strings information can continually be passed between
web pages on a site so that information can be retained.
One of the many beauties of ASP is that the web pages will never
increase in size as the database grows as they are dynamic. Data can
change and the outputted web pages will change, but the original ASP files
will stay the same. Another plus about ASP is that if the script is run on
the server as all the scripts demonstrated do, the programs can be used on
various platforms. As long as the browser can read the HTML, there is no
limit on operating system or machine. Also, since all the ASP files are
generally in one location all the files can be updated easily, so there
are no patches or version updates that need to be released to customers.
ASP is currently being used on E-Commerce sites and other database sites
and it is quickly growing.
