Rails, ActiveRecord, how to find foreign rows that are NOT there?
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Published on 2010-05-28T20:38:30Z
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2010/05/28
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The title is a bit difficult to put together for this question.
Say I have two models, Foo and Bar. Foo has many Bar's. Bar belongs to one Foo. How do I use Foo.find to find all of the Foos that currently have zero Bars? In SQL this would translate into something like:
SELECT * from foo where id NOT IN (select foo_id from bar);
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