Unknown column error

Hello all,

I am getting an unknown column error (mentioned below). What I want to
do
is, extract the language a person speaks. This column is present in the
mhp_register table, and the profile information is present in the
mhp_profile table. I have the following models:

class MhpFriends < ActiveRecord::Base
belongs_to :MhpProfile
def self.table_name() “mhp_friends” end
end

class MhpProfile < ActiveRecord::Base
has_many :MhpFriends
has_one :MhpRegister
def self.table_name() “mhp_profile” end
end

class MhpRegister < ActiveRecord::Base
belongs_to :MhpProfile
def self.table_name() “mhp_register” end
end

The error I am getting is

Mysql::Error: #42S22Unknown column ‘mhp_register.mhp_profile_id’ in
‘where clause’: SELECT * FROM mhp_register WHERE
(mhp_register.mhp_profile_id = 6) LIMIT 1

My index.rhtml file is as follows:

<% @result.each do |res| %>

First name is <%=res.first_name%> Last name is <%=res.last_name%> From state <%=res.from_state%> From city <%=res.from_city%>
Speaks Language *<%=res.MhpRegister.language_speak %>*

<%end%>

The bold area above gives the above mentioned error. Similarly, I also
want
to access all the friends of a profile, so the solution of this problem
will
also help me go about accessing the friends using the same method.

My controller is

class ProfileController < ApplicationController
def index
@result = MhpProfile.find(:all)
end
end

Any insight into this error will be appreciated. Please reply at
[email protected]


Regards

Haris G.

There is no field mhp_profile_id in the mhp_register table, because you
didn’t create one.


Ryan B.
http://www.frozenplague.net
Feel free to add me to MSN and/or GTalk as this email.

But the mhp_register table has a column named “id” and thats what I want
to
use instead of mhp_profile_id. How can I tell rails to look for the id
column and not for the mhp_profile_id column?

On Jan 2, 2008 6:17 AM, Ryan B. [email protected] wrote:

There is no field mhp_profile_id in the mhp_register table, because you
didn’t create one.


Ryan B.
http://www.frozenplague.net
Feel free to add me to MSN and/or GTalk as this email.


Regards

Haris G.

That ID is the id of that mhp_register, not of the mhp_profile.

Also, why must it be called MhpRegister? Why not just Register?

On Jan 2, 2008 3:11 PM, Haris G. [email protected] wrote:

Haris G.


Ryan B.
http://www.frozenplague.net
Feel free to add me to MSN and/or GTalk as this email.

If it’s a one-to-one it still needs to have an mhp_profile_id column,
like I
stated before.

The ID column is specifically for that mhp_register record. You must
create
an mhp_profile_id field in mhp_register.

I’ll also ask this again: Why the MHP prefix?

On Jan 2, 2008 3:33 PM, Haris G. [email protected] wrote:

you didn’t create one.

http://www.frozenplague.net


Ryan B.
http://www.frozenplague.net
Feel free to add me to MSN and/or GTalk as this email.

But the relation between mhp_profile and mhp_register is One-to-One,
hence
the mhp_register has only one column named id, and no foriegn key from
the
mhp_profile table

On Jan 2, 2008 9:48 AM, Ryan B. [email protected] wrote:


Ryan B.
http://www.frozenplague.net
Feel free to add me to MSN and/or GTalk as this email.


Regards

Haris G.

But that means, if mhp_register table is related to several tables with
a
One-to-One relationship, it has to have a mhp_tablename_id column for
each
relation ??

About the mhp prefix, Thats how I got the DB schema. I mean I have to
build
my RoR application on an existing schema, and the existing schema has
mhp
prefix with all tables. Thats how my client requires it.

Please also tell me, If I have three tables named mhp_profile,
mhp_register,
and mhp_friends, and I have three corresponding classes named
MhpProfile,
MhpRegister and MhpFriends. Each profile has_mane friends, and each
profile
has_one register. and both friends and register classes belong to
profile.
Now does rails strictly want EACH profile to have EXACTLY ONE register,
and
EACH profile to have ATLEAST ONE friend ?? I mean is it possible for a
profile not to have any register or not to have any friends ?? Does
rails
stricly enforce the has_one and has_many relationship?

I hope you get my question

On Jan 2, 2008 10:06 AM, Ryan B. [email protected] wrote:

because you didn’t create one.

http://www.frozenplague.net


Ryan B.
http://www.frozenplague.net
Feel free to add me to MSN and/or GTalk as this email.


Regards

Haris G.

Re the mhp prefix:

You don’t have to name your models MhpRegister, you can just call
set_table_name :mhp_register in them. I’m pretty sure there’s a way to
do
this automatically, like in a config file somewhere, but I don’t recall
it.

Re the has_one relationship:

I think you’re misunderstanding how it’s supposed to work. A profile
has_one
register. How does that register know which profile it belongs to?
Rails
will do it by default to the mhp_profile_id field in mhp_register. Set
:foreign_key => “id” on the has_one association and it should work.
Yes it is possible for a profile not to have a register and not to have
any
friends, Rails does not enforce it.

Re the mhp prefix:

Yeah I think we can do it by

def self.table_name() “mhp_register” end

Re the relationships:

Do I set the :foreign_key on belongs_to association or on the has_one
association. I think I tried it with the belongs_to association but it
did
not work. I will try it with has_one association as well. Thanx loads
for
all your help.

Well, I might have been asking some very very basic questions, but I am
actually a starter on RoR. so pardon me with that.

On Jan 2, 2008 10:29 AM, Ryan B. [email protected] wrote:

Rails will do it by default to the mhp_profile_id field in mhp_register. Set
:foreign_key => “id” on the has_one association and it should work.
Yes it is possible for a profile not to have a register and not to have
any friends, Rails does not enforce it.


Regards

Haris G.

Basic questions are fine. That’s what we’re here for.

I was a noob once, and I remember some of the questions I asked and
remember
how I felt when they were answered, so I try to give that feeling to
others.

Could you also please tell me another thing.

If my class name is Profile (and my table name is mhp_profile), Friend
(table name is mhp_friends), and Register (table name is mhp_register)
as
you suggested earlier. And my relations are as I mentioned in my
previous
email (profile has many friends and has one register)

In the profile controller I do @result = Profile.find(:all)

In my view I do

<% @result.each do |res| %>

now if I want to access the friends or the register info using this res
variable, how will I do it ??

On Jan 2, 2008 10:54 AM, Ryan B. [email protected] wrote:


Regards

Haris G.

On 2 Jan 2008, at 05:29, Ryan B. wrote:

Re the mhp prefix:

You don’t have to name your models MhpRegister, you can just call
set_table_name :mhp_register in them. I’m pretty sure there’s a way
to do this automatically, like in a config file somewhere, but I
don’t recall it.

I believe you’re thinking of ActiveRecord::Base.table_name_prefix
Set it to ‘mhp_’ to save some keystrokes.
Fred

Actually here is what Im trying to do…My index.rhtml is as follows

<% @result.each do |res| %>
<%= res.first_name %>


<%= res.register.language_speak %>





<% end %>

My models are as follows

class Profile < ActiveRecord::Base
has_many :friends, :foreign_key => “user_id”
has_one :register, :foreign_key => “id”

def self.table_name() “mhp_profile” end
end

class Friend < ActiveRecord::Base
belongs_to :profile

def self.table_name() “mhp_friends” end
end

class Register < ActiveRecord::Base
belongs_to :profile

def self.table_name() “mhp_register” end
end

But Im getting the following error.

Showing profile/index.rhtml where line #4 raised:

You have a nil object when you didn’t expect it!
The error occurred while evaluating nil.language_speak

Any idea what am I doing wrong…I have only one controller for profile
as
follows

class ProfileController < ApplicationController
def index
@result = Profile.find(:all)
end
end

On Jan 2, 2008 12:45 PM, Haris G. [email protected] wrote:

I was a noob once, and I remember some of the questions I asked and

Regards

Haris G.


Regards

Haris G.

config.active_record.table_name_prefix = “mhp” in your environment.rb
should
do the trick.

On Jan 2, 2008 10:20 PM, Frederick C. [email protected]
wrote:

Yes it is possible for a profile not to have a register and not to
have any friends, Rails does not enforce it.


Ryan B.
http://www.frozenplague.net
Feel free to add me to MSN and/or GTalk as this email.

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