Adding custom fields from DB

Hi,
I would like to add some custom fields to my posts. But there are some conditions:

I would like to take the data from the db and I would like this to be shown only if there’s this data.

For example let’s say I have a review for a game.

I would like to display on the top of the post this fields:

release date
software house

I’ve read the how to field page but is not for data taken from db

bye