database web site conversion to drupal

Does drupal has the limitation of converting a existing web site driven by database (php/mysql) with all existing functionality side.
Does it only do the static content generation and subsequent managing with powerful features.

Are there web sites which are php/mysql database driven and functionalities executed in OOP concept , be able to be converted to drupal with much less effort.
Is it practicable and wise to do this conversion.
Expert Opinion required