Query Strings
There will be times when you don't want the user to have to submit a form in
order to get information. Take for instance, this site. We have a single ASP
page - page.asp, which displays every article or code page on this site. But
you don't have to enter an ID of the article in order to display it! Instead,
the site uses Query Strings. The Query String is a bit of information added
to the end of a URL, and takes one of 2 forms:
http://www.mysite.com/mypage.asp?this+is+some+text
and
http://www.mysite.com/mypage.asp?data1=value&data2=another+value
The latter is the most useful and most widely used.
To access the information sent in the query string, you use the Request.QueryString
property... what a surprise! If, for example, you accessed your page with the
following url:
/mypage.asp?id=4&title=Example+Title
In your ASP page, you could access this information by using Request.QueryString("id")
and Request.QueryString("title"). Take a look at the
following example:
<%
Response.Write "ID: " & Request.QueryString("id")
Response.Write " Title: " & Request.QueryString("title")
%>
Save this to a file called querystring.asp, and view it. At the moment, you'll
see
ID: Title:
This is because no data has been sent in the Query String. Now try adding ?id=876.
You will get
ID: 876 Title:
and finally, add ?id=876&title=My+Title, and you will see
ID: 876 Title: My Title
Query Strings can be especially useful when you need to retreive information
from a database, but need a category ID, for example. Then, you can simply use
Set rData = cConn.Execute ("SELECT * FROM Categories WHERE ID="
& Request.QueryString("id"))
You will, by now have noticed some different characters in the query string.
For example, + replaces a space. However, when you come to access Request.QueryString
it is automatically removed again. If you want to convert a string to a query
string, use Server.URLEncode. For example,
Server.URLEncode("my text & something ?")
becomes
my+text+%26+something+%3F
You can even make your forms generate a query string, so that instead of 'posting'
its data, it generates a querystring instead. To do this, simply remove the
method="POST" text from the form tag.