Delete unused manufacturers?

[benn600]

How can I delete the manufacturers where no products exist? I know it can be scanned on the fly but it really slows everything down so I'd like to just delete them. Or can I hide them? I'd rather delete them.

[kuroi]

Admin > Catalog > Manufacturers

Click on the "i" icon next to each one to see whether they have any products, and if not hit the delete button.

[benn600]

Is there a query I can run? We have over a thousand manufacturers.

[kuroi]

Backup your database first, then (assuming that you are not using a database prefix) run this query

delete manufacturers as m
from manufacturers as m
left join products as p
on m.manufacturers_id = p.manufacturers_id
where p.manufacturers_id is null;

This will delete all manufacturers with no products in your database.