Schema

Even some quality modules by very good developers are still using db_query("DROP TABLE {example_table}"); rather than the schema just defined and properly used by the update.

But sure enough, the hook_uninstall API documentation example shows the use of schema:

<?php
function example_uninstall() {
  drupal_uninstall_schema('example');
  variable_del('example_var');
}
?>

Resolution