display data with a tree

I remember sometimes ago Skrol29 said that display data with a tree or hierarchical structure with levels predefined is much easier when using TBS template. My category table has the levels predefined, and is also the same structure as this: http://www.tinybutstrong.com/forum.php?msg_id=7900#, with a level column.

Could anyone help me how to create a tree structure?

The reason i'm asking for help because I really don't want to use the example from this http://www.tinybutstrong.com/forum.php?msg_id=7900# , because imagine this: if I have 50 categories (including sub-categories), it would execute 50 times in the database, and also merge 50 times, that would slow down for sure.

Thank you all in advance for helping me.

Andy