Does anyone know if there is a way to perform set difference (ie the
elements in set A that are not in set B) using database queries / DAL?
for example if you had some tables defined like this:
db.define_table('thing',
Field('name'))
db.define_table('owns',
Field('person', 'reference auth_user'),
Field('thing', 'reference thing'))
and you want to find a list of all the things that person X doesn't yet own.
The "easy" way would be to query for a set of all the "thing"s and then do
a separate query for all the "thing"s owned by person X, create python set
objects and use the set difference operator.
I'm wondering if there is a way to do this as a single db query?
Thanks!
Paul
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