[Zope-DB] sql method error control

[Aaron Fosdick]

This is as much a tal question as database, but hopefully someone has a 
quick answer. It's prompted by msnbot crawling my site and not following 
query parameters.

Let's say you have a sql method in a page:  
http://xyz.com/form_result_html?param1=value
<div tal:define="results python:here.some_query('param1');">
...
</div>

If a user enters a URL without the parameter 'param1', ex: 
http://form_result_html ,  an error results: name 'param1' not defined.

What is the best way to manage the error? Should I check if the 
parameter exists and assign a value or redirect if it doesn't; and what 
would the tal code look like?

Thanks in advance,

--Aaron