deleting all comments with sql

I have been away from my site for a while and have thousnads of spam comments I need to get rid of. Using the web interface is a pain. I can only increase the number of comments to 40 without error, and it is taking to long. I have a web interface that gives me sql access to the db. I don’t know anything about the schema, so I don’t want to screw anything up. Can someone give me the proper sql commands that will delete all the comments?