[web2py] How to do the following query?

[vortex]

SELECT * FROM item JOIN read on read.of_item=item.id WHERE
item.of_section <> read.of_section

I tried:

db((db.item.id == db.read.of_of_item) & (db.read.of_section !=
db.item.of_section)).select()

but I don't want a join. I just want the where cause to be:
(db.read.of_section != db.item.of_section).