# Find(:all) on parent where child.nil?

**URL:** <https://www.ruby-forum.com/t/find-all-on-parent-where-child-nil/113035>\
**Category:** Rails\
**Created:** [August 26, 2007, 5:08pm UTC](https://www.ruby-forum.com/t/find-all-on-parent-where-child-nil/113035 "2007-08-26T17:08:59Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![jimmyether](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/e9a140/32.png) [@jimmyether](https://www.ruby-forum.com/u/jimmyether)\
**Post date:** [August 26, 2007, 5:08pm UTC](https://www.ruby-forum.com/t/find-all-on-parent-where-child-nil/113035/1 "2007-08-26T17:08:59Z")

</div>

How can I find(:all) on a parent model only for objects where a has\_one  
child is nil?

## Models

class Parent \< ActiveRecord::Base  
has\_one :child  
end  
class Child \< ActiveRecord::Base  
belongs\_to :parent  
end

So, I want to do:

object = Parent.find(:all) where the only rows returned match  
object.child.nil?

I want this to happen on the database level because we will be dealing  
with  
thousands of rows. Is there an ActiveRecord way to handle this, or am I  
going to have to break out to find\_by\_sql for this?

Ryan

---

<div class="post-metadata">

**Author:** ![jimmyether](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/e9a140/32.png) [@jimmyether](https://www.ruby-forum.com/u/jimmyether)\
**Post date:** [August 27, 2007, 10:28am UTC](https://www.ruby-forum.com/t/find-all-on-parent-where-child-nil/113035/2 "2007-08-27T10:28:46Z")

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with\_scope

> **[ActiveRecord::Base](https://api.rubyonrails.org/classes/ActiveRecord/Base.html#M001024)**
>
> Active Record Active Record objects don't specify their attributes directly, but rather infer them from the table definition with which they're linked.

set it to u’r needs 🙂

---

<div class="post-metadata">

**Author:** ![jimmyether](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/e9a140/32.png) [@jimmyether](https://www.ruby-forum.com/u/jimmyether)\
**Post date:** [August 28, 2007, 12:11am UTC](https://www.ruby-forum.com/t/find-all-on-parent-where-child-nil/113035/3 "2007-08-28T00:11:38Z")

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Thanks Shai. I’ve been dipping into with\_scope the last couple of days  
and  
it’s really interesting… especially when it comes to nesting. I’m not  
quite sure how I can utilize it in my situation though where I’m doing a  
left join on two models with a has\_one relationship. Every example of  
with\_scope I’ve seen as been acting within a single model. I’ll keep  
playing  
with it. In the meantime, find\_by\_sql is getting the job done.

On 8/27/07, Shai R. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> >

–  
Ryan W.  
Lead Developer  
Capocus!

> **[Atlanta video production](https://abra.capoc.us/)**
>
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