One of our Drupal sites was misconfigured and as a result it received thousands of spammy comments linking to very undesirable neighborhoods.

Using the Drupal GUI to delete these was taking forever.

Going straight to MySQL was a lot quicker.
SQL Command to Delete all Unpublished Comments In Drupal:
Code:
delete from comments where status = '1';
SQL Command to Delete all Published Comments In Drupal:
Code:
delete from comments where status = '0';
As per usual, back up your database before monkeying with SQL directly.