# ActiveRecord Basics Help

**URL:** <https://www.ruby-forum.com/t/activerecord-basics-help/138024>\
**Category:** Rails\
**Created:** [May 19, 2008, 4:50pm UTC](https://www.ruby-forum.com/t/activerecord-basics-help/138024 "2008-05-19T16:50:52Z")\
**Posts on this page:** 8\
**Page:** 1

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**Author:** ![newbie](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/dc4da7/32.png) [@newbie](https://www.ruby-forum.com/u/newbie)\
**Post date:** [May 19, 2008, 4:50pm UTC](https://www.ruby-forum.com/t/activerecord-basics-help/138024/1 "2008-05-19T16:50:52Z")

</div>

I’m still learning all the cool things about ActiveRecord. I’m  
currently stuck on figuring out how how to make this SQL query into  
something that uses some rails magic.

# Current situation is I have two tables

Entries  
Prizes

class Entry \< ActiveRecord::Base  
belongs\_to :prize  
end

class Prize \< ActiveRecord::Base  
belongs\_to :entry  
end

My logic is that each entry ID has a matching prize ID. If you were to  
look up by prize.id you could find the winning entry using the same  
id. So if you were to do this in MYSQL it would look like this and you  
would get both table rows returned.

# Current MySQL

SELECT \* FROM prizes LEFT JOIN entries ON prizes.id=entries.id WHERE  
prizes.id=“2”

What I’m looking to do is I want the equivalent of the above but  
returning active-record objects, so I could do some edits and save to  
both tables.

# Attempt #1 Doesn’t work

Prize.find(2).entry

Any suggestions?

---

<div class="post-metadata">

**Author:** ![newbie](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/dc4da7/32.png) [@newbie](https://www.ruby-forum.com/u/newbie)\
**Post date:** [May 19, 2008, 5:09pm UTC](https://www.ruby-forum.com/t/activerecord-basics-help/138024/2 "2008-05-19T17:09:17Z")

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On 19 May 2008, at 15:49, newbie wrote:

> belongs\_to :prize  
> would get both table rows returned.

This isn’t what activerecord is expecting. belongs\_to :prize tells  
active record that you entries table has a prize\_id column containing  
the id of something in the prizes table (and similarly for entry). You  
probably could get this to sort of work like this with a :foreign\_key  
=\> ‘id’ option, but expect things to go very wonky if you try to  
delete the associated object, assign to the association etc… More  
generally, if id is an autoincrement column (which rails rather  
assumes) isn’t this going to be a source of endless pain?

Fred

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<div class="post-metadata">

**Author:** ![newbie](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/dc4da7/32.png) [@newbie](https://www.ruby-forum.com/u/newbie)\
**Post date:** [May 19, 2008, 6:34pm UTC](https://www.ruby-forum.com/t/activerecord-basics-help/138024/3 "2008-05-19T18:34:44Z")

</div>

On 19 May 2008, at 17:21, newbie wrote:

> Okay. I see your point. So I’m guessing maybe I should create a tables  
> called “entries\_prizes” to keep track of which entries have a prize  
> associated with them? In the end I just want to be able to query which  
> entries have a prize associated with them BUT by looking it up using  
> the entry ID. I hope I’m making sense, I think I’m making this harder  
> then it needs to be.

I think you are. You haven’t made clear the relationship between  
entries and prizes. You only really need a join table if entries can  
have several prizes and prizes can have multiple entries.

Fred

---

<div class="post-metadata">

**Author:** ![newbie](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/dc4da7/32.png) [@newbie](https://www.ruby-forum.com/u/newbie)\
**Post date:** [May 19, 2008, 6:41pm UTC](https://www.ruby-forum.com/t/activerecord-basics-help/138024/4 "2008-05-19T18:41:18Z")

</div>

I believe your Entry class should be:

class Entry \< ActiveRecord::Base  
has\_one :prize  
end

---

<div class="post-metadata">

**Author:** ![newbie](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/dc4da7/32.png) [@newbie](https://www.ruby-forum.com/u/newbie)\
**Post date:** [May 19, 2008, 6:22pm UTC](https://www.ruby-forum.com/t/activerecord-basics-help/138024/5 "2008-05-19T18:22:21Z")

</div>

Okay. I see your point. So I’m guessing maybe I should create a tables  
called “entries\_prizes” to keep track of which entries have a prize  
associated with them? In the end I just want to be able to query which  
entries have a prize associated with them BUT by looking it up using  
the entry ID. I hope I’m making sense, I think I’m making this harder  
then it needs to be.

---

<div class="post-metadata">

**Author:** ![newbie](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/dc4da7/32.png) [@newbie](https://www.ruby-forum.com/u/newbie)\
**Post date:** [May 19, 2008, 6:48pm UTC](https://www.ruby-forum.com/t/activerecord-basics-help/138024/6 "2008-05-19T18:48:01Z")

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The way it works is as a Entry.new gets created, an ID gets created  
with the Entry, let’s say ID=“2”. When the entry is about to be saved  
it does a lookup on the prizes tables (which are prepopulated) for the  
same corresponding ID=“2”. If it finds the same ID in the prizes table  
we have a winner. It’s easy to return the row using MySQL.

#MySQL example  
SELECT \* FROM prizes LEFT JOIN entries ON prizes.id=entries.id WHERE  
prizes.id=“2”

But I’m trying to do the same thing using Active record and I thought  
this example (see below) would work.

# Doesn’t work

Prize.find(2).entry

---

<div class="post-metadata">

**Author:** ![newbie](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/dc4da7/32.png) [@newbie](https://www.ruby-forum.com/u/newbie)\
**Post date:** [May 19, 2008, 7:12pm UTC](https://www.ruby-forum.com/t/activerecord-basics-help/138024/7 "2008-05-19T19:12:18Z")

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Then I’ll follow rails convention over configuration. Thanks for the  
help.

---

<div class="post-metadata">

**Author:** ![newbie](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/dc4da7/32.png) [@newbie](https://www.ruby-forum.com/u/newbie)\
**Post date:** [May 19, 2008, 6:58pm UTC](https://www.ruby-forum.com/t/activerecord-basics-help/138024/8 "2008-05-19T18:58:07Z")

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On 19 May 2008, at 17:46, newbie wrote:

> But I’m trying to do the same thing using Active record and I thought  
> this example (see below) would work.

Like i said, that’s really not what rails is expecting

belongs\_to :entry, :foreign\_key =\> ‘id’

might work but it probably opens up the door for a lot of trouble. The  
rails way is to have a prize\_id column.

Fred