how classifieds site makes all the posted ad visible to search engines?

I want to create a classifieds site in which t开发者_StackOverflow中文版he ads posted by users are saved in a database. But i want all of the posted ads to be visible in search engines instead of just being displayed on my website. So how do I optimize all data of my database using SEO.

Search engines see web pages. Exactly like your visitors. If an ad is visible on your web page, this page has a URL and this URL is linked to from somewhere, search engines will find it. It doesn't matter whether this web page is static, generated dynamically from database content or written by trained monkeys on the fly, it's all the same if it's a web page.

every classified must be a landingpage, ever landingpage gets communicated to google (i.e.: with a sitemap.xml http://sitemaps.org/)