A table prefix is a prefix you have defined when you installed your database. When you refer to a table in your database, for example the table user, how to you refer to it when you run a query? Do you call it "user" or something like "vb3_user" or "mydb_user"?
Try running the above query as shown below:
Code:
ALTER TABLE `user`
add `warnings` int(5) default '0',
add `warning_level` int(15) default '0',
add `warning_bans` int(2) default '0',
add `alerts` int(5) default '0'
Rgds