[Zope] Problem: form-checkbox -> MySQL-table

I got a MySQL-table with lots of "boolean"-values, in the form of ENUM('Y',N'). In my webpage I got a bunch of checkboxes and I want to map the checkboxes to the fields in the table. The problem is that a checkbox-value is only available if the checkbox has been checked. I've tried using <dtml-if fieldname> in my sql to check for the presence of a checked checkbox, add it to the columns-list and value-list if present, but I get an error " Error Value : 1136, "Column count doesn't match value count at row 1". That would be ok, if I could just see the SQL-statement that didn't work. In short : how can I post a bunch of boolean-like values from a form to a sql-method using MySQL? Thanks in advance, Thomas