You can use a simple JavaScript timer to execute a function on a set interval:
http://www.w3schools.com/js/js_timing.asp[
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You can use jQuery to easily load/replace content in an HTML element, using POST:
http://api.jquery.com/jQuery.post/[
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Put the .post() call in your timer and update your page in the response. Your server will need a script that exposes a bit of HTML that you can put into your page on each request. That script will need to access your database.
If you're having trouble getting any of these pieces going, feel free to create new questions with specifics.
Cheers.