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Programming i!-Database Plus
James R. Groff and Paul N. Weinberg. If you like to read on the web, surf to:
http://www.informix.co.za/answers/english/docs/visionary/infoshelf/sqls/sqls.ix.html.
Another option is to read the Microsoft Access
information regarding SQL into the help file.
If you are familiar with Access, build the queries in Access and switch to the SQL view from the
View menu to see what you built. This provides a simple and intuitive way to build your SQL.
The last and easiest option is to use AMX's DBWizard program. This program peeks into your
database and helps you build the SQL to read and write to any of the tables or views in the database.
It also generates a large amount of the NetLinx code for you, so your development time is greatly
reduced. This program is available from www.amx.com.
HTTP, CGI and XML
HTTP (Hyper-Text Transfer Protocol)
An example URL to retrieve records 1 - 5 from a table called Titles is:
http://server/databasescript.asp?SQL=SELECT * FROM Titles&Ps=5&start=21
where:
server
databasescript.asp
?SQL=SELECT * FROM
Titles&Ps=5&start=21
You can use a URL like this to run a query directly against the server script, like the NetLinx
system. This is often useful during testing to make sure the server script is operating properly.
If you do use a URL like this, you will notice that once you hit enter, the spaces are
replaced with %20. URL's have a certain set of characters that are excluded from
normal use. These include space, question mark, ampersand, slash and colon. The
reason for this is these characters are used in other parts of URL's. To use them
again would cause confusion during URL parsing. One of the functions in the
NetLinxDBInclude.axi file takes care of this conversion for you.
CGI (Common Gateway Interface)
CGI provides a simple way to pass parameters to a program from an HTTP request. Most
commonly, the CGI parameters appear directly on the URL line. For example:
http://www.somehost.com/index.htm?myname=amx&myhometown=dallas. The first part of
the URL looks familiar: it contains a protocol, a host name and a file to retrieve
(protocol = http://, host=www.somehost.com, file=/index.htm). The last part is CGI. CGI
parameters are passed in name-value pairs separated by an "=". The "?" is used to signify the start
of CGI parameters. The "&" is used to separate CGI parameters. So this URL contains two CGI
parameters: the first is a CGI parameter called myname and contains a value of amx. The second is
myhometown and contains a value of dallas. The CGI application on the web server has access to
these variables and can use them to help understand the context in which the request was made.
6
®
help file. Microsoft has put a lot of good
Name of web server
Name of server script
CGI Parameters
i!-Database Plus and DBWizard
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