RDBTools (http://www.zope.org/Members/k_vertigo/Products/RDBTools Provides for pythonscript accessible functions to perform set operations on zsql method results. Operations provided - union_results - join_results - difference_results The algorithms are based off Aaron Watters kjbuckets package and his early 1995 news posting to comp.lang.python. Example Use Case You have correlatable data in multiple dbs. Lets say employee contact info is in postgres, and payment info is in oracle. You want to aggregate this info into a single result set for a report display. a contrived example but a useful illustration. contact table: create table corp_employee_contacts ( employee_id integer unique not null, email varchar(255), first_name varchar(30), last_name varchar(30), middle_name varchar(30) ); payment table: create table corp_employee_accounts ( employee_id integer unique not null, payment_period integer not null, payment_amount numeric default 0 not null ) zsql method: getEmployeeContacts: select * from corp_employee_contacts zsql method: getEmployeeAccounts: select employee_id, sum(payment_amount) as total_pay from corp_employee_accounts group by employee_id python script getEmployeeTotalPay: from Product.RDBTools import join_results contacts = context.getEmployeeContacts() accounts = context.getEmployeeAccounts() return join_results(accounts, contacts) the resultant result set contains properly merged information from both results Advanced Usage Note Acquisition Contexts ZSQL Results sets are bound to a context, the set operations exposed here preserve the context of the first result set argument. Brains brains are not preserved. Speed additional speed can be had by using installing the kjbuckets extension module, if its not installed the python implementation found in zope will be used. Cross Products if no common columns are found a cross product is returned. Author kapil thangavelu License X11, see LICENSE.txt for more details