Where does Drupal 7 store custom user account fields? I imported 8500+ external users from an external user table using Feeds module successfully. Now, I am trying to add some more attributes to these users (ie. age, gender, ...). I proceeded to create several new fields for my users under admin/configuration/account settings/manage fields (ie. Age, Gender, ...). However, these fields are now all empty and it would not be possible for me to manually edit these fields for all users.

Could someone please tell me where D7 stores these new fields in the database (which table)? I would like to use a SQL script to automatically update the users with these fields.

PS. Is using a SQL script to update these information the correct approach?
Assuming you're using the SQL storage backend they're stored in the field_data_field_FIELDNAME and field_revision_field_FIELDNAME tables. The field system in Drupal 7 is generic across all entities so field data for nodes/users/all entity types is stored in the same tables.

Rather than input directly into those tables, though, I'd suggest using the Drupal API to load, alter and then save each user instead. The code might look something like this:

// Grab all the uids in the users table
$uids = db_query('SELECT uid FROM {users}')-&gt;fetchCol();

// Load the users
$users = user_load_multiple($uids);

// Loop through and edit each user
foreach ($users as $user) {
  // Load the extra data from whatever source you're using
  $extra_data = my_function_to_get_extra_data_by_user_id($user-&gt;uid);

  // Update the fields
  $user-&gt;field_FIELDNAME1[$user-&gt;language][0]['value'] = $extr_data['FIELDNAME1'];
  $user-&gt;field_FIELDNAME2[$user-&gt;language][0]['value'] = $extr_data['FIELDNAME2'];
  // etc...

  // Save the user object
  user_save($user);
}


You'll probably want to change this code to process the users in batches as it's likely to take a long time to run.