tommytx on "How to stop allowing posting for pages and posts that are done."

I found the command in the discussions to prevent comments on all new postings.. but is there a way to prevent comments on all the pages and posts that are already done.... short of exporting the data and changing the comment authorization and then import it back in or going to Mysql and make the change... Thanks for any advice..
IF I have to do it in mysql does anyone know what field to change and to what.... Thanks..