Magento tutorial to work with product collections and databases

Question

looking for tutorial to work with product collections like,

Upsell products (just an example),
Grouping upsell products by categories,
accessing databases and get items by magento's MVC.

Sharing relevant tutorials is much appreciated.

Answer 1

There are many tutorials available.

Start with these:

Product Types in magento

Related products, Up-sells, Cross-sells in Magento

Product Collections in Magento