Tables: Unnecessary duplication of id fields

=begin

Hello,

I’m fairly new to Ruby, but I am trying to understand the relationship
between database structure and models.

My difficulty is that I have five or so tables all linked together and
their
primary key column is a serial number

The tables are a set of tables called:

itemmasters
products
prices
subprices
imprints
etc.

products, prices, and subprices, imprints, etc. belong to itemmasters
based
on a serial number

How can I get about linking them without having to have a column in
itemmasters for each of the sub tables?

For instance:

product_id
price_id
subprice_id
imprint_id

This would be somewhat silly as they all contain the same information.
Right?

Thank you,

Brian A.

=end

On Mon, Jun 30, 2008 at 11:09 AM, brian [email protected] wrote:

The tables are a set of tables called:

This would be somewhat silly as they all contain the same information.
Right?

Thank you,

Brian A.

=end

While not really a Ruby or Rails question, it seems you have
rows/tuples that point to a singular row in another table. In other
words, reverse it. Have columns in your “subtables” that is the
foreign key of the “master” one.

It’s possible I misread your question, though. I do that pretty
frequently :slight_smile:

Todd

=begin
Thank you for the response.

Maybe it will be clearer if I will just begin with the symptom.

I am getting an error saying “Couldn’t find Itemprice without an ID”

This message comes up even despite the fact that this is my controller:

class ItempriceController < ApplicationController
def show
@itemprices = Itemprice.find(params[:ItemSerial])
end
end

I am not finding Itemprice by id according to the above, but still I get
this error.

In my view as a test I have the following:

<% @page_title = “#{@itemprices.Price1}” %>

-Brian

----- Original Message -----
From: “Todd B.” [email protected]
To: “ruby-talk ML” [email protected]
Sent: Monday, June 30, 2008 11:29 AM
Subject: Re: Tables: Unnecessary duplication of id fields

=end

On Mon, Jun 30, 2008 at 12:10 PM, brian [email protected] wrote:

end

I am not finding Itemprice by id according to the above, but still I get
this error.

In my view as a test I have the following:

<% @page_title = “#{@itemprices.Price1}” %>

-Brian

Hmm. I’m no Rails expert, but maybe you should check the type/class
of the object params[:ItemSerial]. Just a thought. Also, your
database setup may be strange for Rails as I alluded to earlier. I’ve
actually had this error a few times before, but can’t remember how I
fixed it :confused:

Todd

Thanks all for the response. I will have to play with it some more this
week, and update with how it goes…

On Mon, Jun 30, 2008 at 2:38 PM, Todd B. [email protected]
wrote:

end
-Brian

Hmm. I’m no Rails expert, but maybe you should check the type/class
of the object params[:ItemSerial]. Just a thought. Also, your
database setup may be strange for Rails as I alluded to earlier. I’ve
actually had this error a few times before, but can’t remember how I
fixed it :confused:

Todd

It sounds to me like Itemprice.find(params[:ItemSerial]) is returning
nil
for whatever reason. This is getting passed along and then rails is
trying
to retrieve the item from the database using nil for the id in your
view.

If you are doing a find with one argument rails assumes that argument
evaluates to an id value. If you want to match on a field you would
need
something like find(:all, :conditions => [“serial = ?”,
params[:ItemSerial]])


“Hey brother Christian with your high and mighty errand, Your actions
speak
so loud, I can’t hear a word you’re saying.”

-Greg Graffin (Bad Religion)

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