The other day on my personal website, rjfc.net, I found out that I had 10,000 spam comments. They had all been accepted and there was no way I could manually delete each one. I was looking on the web for about an hour and stumbled across an article on how to delete all accepted comments. Here is the link to the article: http://www.blogopreneur.com/2009/04/08/mass-delete-pending-comments-from-wordpress/
If that doesn’t work for you, try using this query: << DELETE FROM wp_comments WHERE comment_content LIKE “%WORD%” >> Replace WORD with the keyword of the keywords that are mentioned in the comments you want to delete.
This is really useful if you are having trouble with your spam comments on WordPress. Make sure you take precautions on wp-admin to make sure it doesn’t happen again.