# Managing a lopsided has\_and\_belongs\_to\_many relationship

**URL:** <https://www.ruby-forum.com/t/managing-a-lopsided-has-and-belongs-to-many-relationship/117736>\
**Category:** Rails\
**Created:** [October 19, 2007, 8:29pm UTC](https://www.ruby-forum.com/t/managing-a-lopsided-has-and-belongs-to-many-relationship/117736 "2007-10-19T20:29:02Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![dmorin](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/f0a364/32.png) [@dmorin](https://www.ruby-forum.com/u/dmorin)\
**Post date:** [October 19, 2007, 8:29pm UTC](https://www.ruby-forum.com/t/managing-a-lopsided-has-and-belongs-to-many-relationship/117736/1 "2007-10-19T20:29:02Z")

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I’ve got a fixed list of several thousand Things, and a User base that  
may grow to who knows how big (we can only hope ,right?) Users have and  
belong to many Things. I want to display a list of top Things, based on  
how many users each has. Things with 0 users are not displayed.

Two questions. First, I expect the density of the relatioships to focus  
on a small percentage of the things. So while I may have 10,000 of  
them, it might be true that only 100 have at least 1 user. In doing my  
find statements, what would the syntax be to say “I am only interested  
in Things where users.size \> 0”? I’m hoping that I odn’t have to get  
them all and simply choose not to display 90% of them, that seems like  
unnecessary moving around of data.

Second, my goal is to sort these Things for presentation by users.size()  
descending. Can I push my luck and get that out of the initial find  
statement, or do I have to do my own sort?

Thanks!

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<div class="post-metadata">

**Author:** ![dmorin](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/f0a364/32.png) [@dmorin](https://www.ruby-forum.com/u/dmorin)\
**Post date:** [October 19, 2007, 8:40pm UTC](https://www.ruby-forum.com/t/managing-a-lopsided-has-and-belongs-to-many-relationship/117736/2 "2007-10-19T20:40:21Z")

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Duane M. wrote:

> I’ve got a fixed list of several thousand Things, and a User base that  
> may grow to who knows how big (we can only hope ,right?) Users have and  
> belong to many Things. I want to display a list of top Things, based on  
> how many users each has. Things with 0 users are not displayed.
> 
> Two questions. First, I expect the density of the relatioships to focus  
> on a small percentage of the things. So while I may have 10,000 of  
> them, it might be true that only 100 have at least 1 user. In doing my  
> find statements, what would the syntax be to say “I am only interested  
> in Things where users.size \> 0”? I’m hoping that I odn’t have to get  
> them all and simply choose not to display 90% of them, that seems like  
> unnecessary moving around of data.
> 
> Second, my goal is to sort these Things for presentation by users.size()  
> descending. Can I push my luck and get that out of the initial find  
> statement, or do I have to do my own sort?

I’d recommend using a has\_many :through if you’re doing stuff like that.  
Here’s an old article I wrote on doing something similar (should be  
updated RSN for 2.0) that should be enough to get you started…

[http://blog.hasmanythrough.com/2006/6/12/when-associations-arent-enough-part-2](http://blog.hasmanythrough.com/2006/6/12/when-associations-arent-enough-part-2)

The counter\_cache functionality has been beefed up some since then, and  
you may find that useful too.

happy friday…

–  
Josh S.  
[http://blog.hasmanythrough.com](http://blog.hasmanythrough.com)