[Zope] dtml-sqlgroup where question

[Juergen Gather]

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