[Zope] dtml-sqlgroup where question

I'm looking for an easy way to find out, if dtml-sqlgroup where generated a where clause or not. Problem: If nothing is entered in my search form, there is no where-clause and I get all DS as result - what I'm looking for is way to add something like where 1=2 if there is no where clause generated by dtml-sqlgroup where - of course I could check each of my 64 input fields ;-) if they were all left blank but I hope there is a better way do achieve this. Any hints ? Thank you, Juergen