ActiveRecord: inverse of includes (find all with no nested object)

Question

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Rails 3 finding parents which have no child

I need to find all objects that does not have a nested object attached.

I'm aware of User.all.includes(:address) includes all with an "address" nested object but I'm not sure how to do the opposite.

The schema looks something like this. There's no User.address_id attribute.

User
has_one :address

Address
belongs_to :user
user_id: integer
address: string

Why its needed? I expect only to check for `User.address` nested object presence. — Martin, Nov 19 '12 at 06:22

score 1 · Answer 1 · answered Nov 19 '12 at 09:00

Okay. I made a stupid mistake in the previous answer.

Here is a proper solution. You could do a query to find the Users with addresses then you can filter the Users without the address by passing the result of the previous query to another query.

Do this:

User.find_by_sql("SELECT * FROM users WHERE users.id NOT IN (SELECT users.id FROM users INNER JOIN addresses ON users.id=addresses.user_id)");

Btw this is a good question. Wonder why it was down voted.

ActiveRecord: inverse of includes (find all with no nested object)

1 Answers1