okay, then the error indicates that *that* statement has already been run to update the database.
Specifically this line, which is contained in a gang of new columns being added in one statement:
Code:
ADD `po_sent` char(1) NOT NULL default '0',
Given that *that* particular statement (all of what you quoted) has already been run, you won't be able to run it again without getting the error you reported. You might want to remove those lines from the group of statements you are trying to run, and submit the rest (essentially starting with the next statement *after* the part you just quoted).