How to extract data from DB into fields?
If you just want the content, you can use Feeds as Patrick said but this will replicate the content of the other database as entities in your Drupal site.

If you really want views connecting to a remote database, this question looks like a duplicate of:

https://drupal.stackexchange.com/questions/3275/how-do-i-display-an-external-database-data

This will help you make Drupal "aware" of the external db:

http://drupal.org/node/18429