oddity with insert multiple input fields to multiple tables

I have a web page interface to a mysql database. In this web page I have about a dozen form input fields. On submit these are submitted to multiple tables, a differant table for each input field. If I leave any fields blank, and insert only some of the fields, the database will insert an empty row to all the effected tables that didn't have any data from the input fields. I have another page that generates graphs from the tables, the empty rows show up as breaks in the graphs lines, if I manually delete all the empty rows the graphs work fine. What do I need to do to prevent these empty rows from being written to the tables? -- chip w www.wiegand.org chip@wiegand.org (my web server died and the hard drive crashed hard, and is running from an incomplete backup on another machine, what a drag) :-(