Help with Foreign Keys

[eluser]GSV Sleeper Service[/eluser]

You can only use a foreign key in an InnoDB table (at least in MySQL)

not true, you can only use foreign key constraints in an InnoDB table. There's no actual way of knowing that a column is a foreign key in a MyISAM, but you can still set them up as such, it just won't inform you that you are about to destroy the referential integrity of your DB when you try to do something silly (like deleting a comment that is still referenced in your posts table)