Switch to a working theme via the database after deleting a theme leads to WSOD

OK, maybe there are other situations where this can come up but in this case my esteemed colleague deleted the only enabled theme. This resulted in a White Screen Of Death (WSOD). A database fix was about as fast and more what was wanted (the deletion was intentional, just not the WSOD) than rolling back to a version with that theme (called mydeadtheme here to protect the innocent).

From the command line on your test server or local development environment:

mysql -u root -pMySEcretPass
If your username and password is correct (it doesn't have to be root; in fact you can use the MySQL username and password in your settings.php or db.php file) you will be greeted with the mysql prompt, mysql>.

SHOW DATABASES;
USE drupal_mydatabasename;
SELECT name, status FROM system WHERE type='theme';
UPDATE system SET status=1 WHERE name='garland';
UPDATE system SET status=0 WHERE name='mydeadtheme';
TRUNCATE cache;
TRUNCATE cache_page;

That was it. You have your site back. Not sure everything was necessary. And everything after the first command was at the mysql> prompt of course.

Then you can EXIT; to return to your shell.

Resolution