WordPress MU

We have a teacher who wasn't watching his comments waiting in moderation and now has 34,000 spam comments. Most are inappropriate or sales pitches. Is there a place on the blog or on the blog server where you can delete all the spam messages at once?

you could write a script to query the db for comments marked as spam and delete them.

I can post an example if you need it. Also I would recommend using reCaptcha, I use it and it works like a charm to stop spam comments.

http://wpmudevorg.wordpress.com/project/WP-reCAPTCHA

<?php
global $wpdb;
$removespam = 'DELETE FROM wp_X_comments WHERE comment_approved="spam"';
$wpdb->query($removespam);
?>

the X above should be replaced with the blog number of the person you want to remove spam messages from.

Also wait for one of the experts to approve this method I would hate for it to cause unknown problems. I am just thinking that is how I would do it.

I use it and it works like a charm to stop spam comments.

...as well as those who can view those images either because they can't see them or they're behind some sort of proxy.

If you;re not currently using any solution, you may want to give this a read:

http://wpmututorials.com/plugins/stopping-spam-comments-sitewide/

Try this method though to solve your issue:

http://articles.rootsmith.ca/wordpress/deleting-massive-amounts-of-comments-in-wordpress

If you are using some sort of method to combat spam where the comments are already marked as such, the software changes "comment_approved" to 'spam'. You can use the SQL mentioned in that article. I'd just do the check against "comment_approved" instead of looking for terms.

Bother Typepad Antispam and Akismet have a check box that will autodelete spam after I believe 15 days. You may want to suggest that to anyone who doesn't keep up on that sort of thing.

If it is all in one blog, just go to Comments -> Spam -> delete all spam. One click and they are gone :)

Oh, that's just too easy ;) I knew there was a better solution than my own.

Let say you delete a spam comment, this is not going to break a member's blog? Or let say you delete a spam blog post, this is not going to break a member blog too? Or how about let say delete a single spam blog from a member, this is not going to break the wpmu as a whole? By the way doing all this inside mysql or phpmyadmin I meant.

As long as you know what you are doing then, no it's not going to break anything.

You may get an error about missing comments but the system (edit: meaning wpmu) should correct itself.

Know a link that I can read on how WPMU's database works? I need to understand its inside out for me to work with it efficiently and less error prone. Thank You!

Why are you deleting these thing right out of the databse? Why not from the backend?

Only do it via the database if you:
a) have a LOT to delete
b) can run a SQL statement to do so
c) know what you're doing

Because that kind of work is a whole lot more in the realm of database theory & management and less about WPMU in particular.

That being said, a short article from the codex:
http://codex.wordpress.org/WPMU_Database_Description