Netscape Communications Corporation created the first version of cookies on the Web, and the specification posted at http://home.netscape.com/newsref/std/cookie_spec.html, while incomplete and a bit out of date, is a good introduction to the subject.
For a more complete treatment of the topic, you should look at RFC 2109, the Internet standards document that describes the use of cookies in far greater detail. Many sites mirror Internet RFCs; one such site is http://www.internic.net/, the home page of the body that assigns domain names in the United States.
For an introduction to the use of cookies, as well as some sample code, take a look at http://www.illuminatus.com/cookie.fcgi/.
Finally, CGI programmers using CGI.pm should read the well written documentation for that module, which includes some basic information on how to handle cookies from within your programs. CGI.pm, like nearly all Perl modules, is available via CPAN (the Comprehensive Perl Archive Network). You can find the closest CPAN mirror site to your Internet connection by pointing your browser to http://www.perl.com/CPAN/.
SQL-related information in this column, should be largely compatible with all relational databases. It was tested under MySQL, a “mostly free” relational database that runs under Linux. You can find out more about MySQL, including documentation and a fully enabled downloadable version, from the author's web site at http://www.tcx.se/.