A very simple approach could be Querylet with Querylet::CGI. This lets you enter parameters and run an SQL query on a server.

This assumes that you already have an HTTP server that can run CGI scripts and DBI with the appropriate database driver (likely DBD::ODBC, DBD::Oracle, DBD::mysql or DBD::SQLAnywhere)

Hello TCLion,

Reading this tutorial (Perl DBI - Put Your Data On The Web) and (Introduction to retrieving data from your database - Perl DBI/DBD::ODBC Tutorial Part 2) would be a good start.

How do I get the HTML text fields to complete a query

• how much HTML do you know?
• can you create a HTML <form> with <input> fields?
• as far as i know you will need a web server to process a <form> do you have a web server and do you have permissions to write to the cgi-bin libraries?

run the query, SQL I think

I mostly use DBD::SQLite a subset of DBI, but at times use DBD::mysql.

All the DBI routines share the same query model. first you connect

my $dbh = DBI->connect("dbi:SQLite:dbname=$dbfile","","");
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$sth = $dbh->prepare("SELECT foo, bar FROM table WHERE baz=?");
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  $sth->execute( $baz );
  while ( @row = $sth->fetchrow_array ) {
    print "@row\n";
  }
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display results on the same HTML I started with?

Well that isnt quite true, you get some HTML, fill in the form, press the submit button, then you get NEW HTML back. But it will probably be from the same address. For the most part the same cgi code will first construct the page with the empty form, then when you press submit get the input from your browser, execute your sql from the input fields, then construct a page with the results and another form.

I don't know how much experience you have in perl, web and database, so here's the basics - the requisites and a simple script to get you started. You need:

• a configured web server which allows CGI scripts
• a database server
• the modules DBI and CGI

The html page comprises a form with a method, and some inputs. The browser sends the input names along with their values to the webser server, which parses the request and provides the name/value tupels to the script, depending on the request method:

• GET = via the environment variable QUERY_STRING (see %ENV)
• POST = via the standard input file descriptor STDIN

You take these request values and query the database with them, then you send the results back.

So, you could roll your own parsing of the query like so:

my $query;
if ($ENV{REQUEST_METHOD} eq 'GET') {
    $query = $ENV{QUERY_STRING};
} elsif ($ENV{REQUEST_METHOD} eq 'POST') {
    read STDIN, $query, $ENV{CONTENT_LENGTH},0;
}
# make a hash from the query
my %param;
my @tupels = split /(\&|;)/,$query;
for my $tupel(@tupels) {
    my ($key,$value) = split /=/, $tupel;
    $param{$key} = $value;
}
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but this is highly discouraged since this basic code, provided as an example only doesn't handle all edge cases (e.g. multivalue parameters) and could make your script vulnerable. Better (not best, though) is using the CGI module.

The following script provides a simple form, and the results of the query, if valid POST data has been sent along with the request.

You need a table persons in the test database on your SQL server, like so:

CREATE TABLE persons (
    name varchar(255),
    age tinyint
);
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and of course, fill it with some values.

Change the username and password below to reflect your setup.

#!/usr/bin/perl -T # always use -T for CGI stuff. read perlsec

use strict; use warnings;
use CGI qw(:standard); # this pulls in param(), header() and start_htm
+l()
use DBI;

my @query_results;
my $error;
my $name;
# if we have a 'name' param, check it...
if (param('name')) {
    if (param('name') =~ /^(\w+)$/) {
        $name = $1;
    }
    # ...and if name param is ok query the DB
    if ($name) {
        my $dbh = DBI->connect(
            "DBI:mysql:database=test",
            'testuser', # username - change to your setup
            'secretpw', # password - change to your setup
            {RaiseError => 1},
        ) or $error = "could not connect to database";
        my $sth = $dbh->prepare(
            "select name, age from persons where name = ?"
        );
        $sth->execute($name);
        while(my $row = $sth->fetchrow_arrayref) {
            push @query_results, $row;
        }
    }
} else {
    $error = "please enter a valid name\n";
}
print header(), start_html('SQL Query');
print <<EOH;
<html>
<head><title>SQL</title></head>
<body>
<h1>SQL Query</h1>
<form method="POST" action="/cgi-bin/sql.cgi">
<input id="name" name="name"/>
</form>
<hr>
<table border=1>
<thead><tr><td>Name</td><td>Age</td></tr></thead>
<tbody>
EOH
foreach my $row (@query_results){
    my ($name, $age) = @$row;
    print "<tr><td>$name</td><td>$age</td></tr>\n";
}
print "</tbody>\n</table>\n";
print "<b>$error</b>" if $error;
print "</body></html>\n";
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See perlsyn, perldata, perlvar, perlsec; read perfunc, perlref, perlreftut ...well, read the complete perl documentation ;-). Read the CGI and DBI manual pages.

There are complete web frameworks to be found on the web for CRUD operations (create/read/update/delete) which you should consider if your project comprises more than simple queries, and as your familiarity with perl grows.