[Zope] ZCatalog: searching where on index == another index

Hi all, Is there a way to search for all the records where one indexed field equals another indexed field? Equivalent SQL query would be: SELECT * FROM table WHERE field1 = field2 I know I can get all the unique values for field1 and then do a search for records where field2 = [unique field1 values], but isn't there a better way? Etienne