How to import external database table into Drupal database table? I imported an external database into my local Drupal database. The database table I am particularly interested in is the default "users" table in Drupal and the imported "USER" table from the imported database (My current Drupal database has both "users" and "USER" tables).

The external "USER" table contains columns that are not contained in my current Drupal "users" table.

I would like to perform either one of the following:


Merge the "users" and the "USER" table, so that all the rows from the "USER" table is now contained in the "users" table.
Allow Drupal to obtain login information from the externally imported "USER" table. By this, I mean if there is a user called "ABC" in the "USER" table, then Drupal should allow user ABC to log into the website.


Any help is appreciated. Thank you.

EDIT:

I have tried using the migrate module, but nothing shows up nor do any options show up for me to migrate my data. I have found a little tutorial that teaches how to import external data using drush and migrate - http://www.gizra.com/content/data-migration-part-1. Is this the correct way to use Migrate?
You have at least 2 choices, none of which is easy in my opinion.


Import the non-drupal-users into drupal using a tool such as Migrate to actually map the new fields into drupal fields, you can use hook_schema_alter() and hook_entity_propery_info_alter() to tell Drupal about these new fields that Migrate is moving over.
If you dont merge these tables permenantly into 1 drupal "users" table you're kinda making more trouble for yourself. You could implement your own authentication method to do an SQL query against your (non-drupal) Users table and if the visitor is found there create a new Drupal user account for them. To do so you'd basically create your own login logic as loosely described here for an external source, Blog Tutorial