Ruby on Rails

On Sep 29, 2011, at 8:56 PM, maskiran wrote:

> I have the following tables
>
> create table files(id int ai pk, name varchar(255)
> create table admins (file_id int, user_id int)
> create table users (id int ai pk, name varchar(16),email varchar(255))

And presumably classes like:

class File
has_many :admins
has_many :users, :through => :admins
end
class Admin
belongs_to :file
belongs_to :user
end
class User
end

>
> I want to get all the admin user names and emails of a given file. Say
> for file 1

File.find(1).users

or

File.where(:id => 1).users

>
> Admin.where(:file_id=>1).includes(:user). it works very good. Now I
> want to sort the admins on the usernames

Then add and .order('users.name') to the query.

Alternatively, you could always get the users in that order:

class File
has_many :admins
has_many :users, :through => :admins, :order => 'users.name'
end

>
> Admin.where(:file_id=>1).include(:user).order('users.name'). this
> shows an sql query with an empty column and so bails out. here's the
> query I got on the console
>
> SELECT `admins`.`` AS t0_r0, `admins`.`file_id` AS t0_r1,
> `admins`.`user_id` AS t0_r2, `users`.`id` AS t1_r0, `users`.`name` AS
> t1_r1 FROM `admins` LEFT OUTER JOIN `users` ON `users`.`id` =
> `admins`.`user_id` WHERE `admins`.`file_id` = 1 ORDER BY users.name
>
> The first column name is being taken as empty (immediately after the
> select).
>
> Is this a bug? I don't want to have id field in the admins table as
> that's not useful. How do I write a AR query to sort out this issue
>
> thanks
> Kiran

You should not need an `id` on the admins table, but you almost
certainly want to have an index on each of the `file_id` and `user_id`
columns.

-Rob

Rob Biedenharn
Rob@AgileConsultingLLC.com http://AgileConsultingLLC.com/
rab@GaslightSoftware.com http://GaslightSoftware.com/

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