Drupal as an interface for users to Add/Edit/Search a database
Start off with something like this:


Build Content Types for the data you want to represent. Remember that relationships in Drupal are different than the DB world and are joined with things like http://drupal.org/project/relation or http://drupal.org/project/entity_reference
Use a module like http://drupal.org/project/migrate or http://drupal.org/project/feeds to import your data and map it into your nodes. Feeds will handle what you're doing here pretty handily but if you need more advanced manipulation on the way in, Migrate is the way to go. This can basically run on some kind of cron/batch to continue a "sync" of your data.
Use http://drupal.org/project/views to build reports of your data


If you need to manipulate the data tables directly, that's not exactly what Drupal is built for. It's more than a Front End. It's a full CMF.