Define a unique primary key based on 2 columns
In Rails 5 you can do the following:
create_table :words, primary_key: %i[id language_id] do |t|
t.integer :id
t.integer :language_id
t.string :value
t.timestamps
end
It is also NOT necessary to set the primary_key
attribute on the Word
model.
add_index :words, ["id", "language_id"], :unique => true
It should work. Maybe you have already some non-unique data in your db and index can't be created? But (as @Doon noticed it will be redundant since id is always unique). So you need create primary key on two columns.
To define 2 column primary key in rails use:
create_table :words, {:id => false} do |t|
t.integer :id
t.integer :language_id
t.string :value
t.timestamps
end
execute "ALTER TABLE words ADD PRIMARY KEY (id,language_id);"
And set primary_key in your model with this gem: http://rubygems.org/gems/composite_primary_keys:
class Word < ActiveRecord::Base
self.primary_keys = :id,:language_id
end
As I said in my comments you will be fighting rails if you try this, and it isn't really supported out of the box. you can look at http://compositekeys.rubyforge.org which offers a way to do composite primary keys in rails. I haven't used it, as I haven't had a need yet (normally when I have something that is composite key like it is just a join table with no primary key and a unique index on the joined pair (HABTM).
Model
class User < ActiveRecord::Base
has_secure_password
self.primary_keys = :name
end
Migration
class CreateUsers < ActiveRecord::Migration
def change
create_table :users do |t|
t.string :name, null: false
t.string :emailid
t.string :password_digest
t.integer :locked, :default => 0
t.text :secretquestion
t.string :answer
t.timestamps null: false
end
add_index :users, :name, :unique => true
end
end
You will get this table