CODEWITHSUNDEEP
ruby-on-railsruby-on-rails-4
Rasheed
Rasheed

Reputation: 35

Generate a Migration to Create a Table that Joins 3 Tables

I have 3 tables and I want to create new table that stores the following:

user_id 
project_id 
company_id

I've tried through this command, but it does not work:

rails g migration CreateJoinTableUserProjectCompany 
    user:referencess project:referencess company:referencess

What do you recommend?

Upvotes: 1

Views: 113

Answers (3)

Joe Kennedy
Joe Kennedy

Reputation: 9443

I'm not actually sure how generate the migration to create a join table with only those three columns, and id column. Obviously we can edit the generated migration and edit it (which I'll do in my answer), but where's the fun in that?

That having been said, and all fun apparently removed, I'd suggested creating an entire table, including id column, even though you may not think you need it. It may come in handy (which of these two u-p-c's was created first, I need to put this model in a nested form, etc.). To create a table that includes the id, you can simply run the following command.

rails g migration CreateUserProjectCompany user:references project:references company:references

Running the created migration will create a table that looks like:

id | user_id | project_id | company_id

To create the table without id, you'll unfortunately need to edit the migration. Replace this line...

create_table :user_project_companies do |t|

...with this one.

create_table :user_project_companies, id: false do |t|

I.E., add , id: false after the table name, which specifies that the table should not have an id column. Running this migration will give you that table with only the three columns.

user_id | product_id | company_id

Upvotes: 1

San
San

Reputation: 1954

Generating a migration alone does not use the column parameters unless you want to add or remove a column to an existing model. You would need to generate a model to accomplish what you are trying to do (almost). For example:

rails g model UserProjectCompany user:references project:references company:references

This will generate following migration:

class CreateUserProjectCompanies < ActiveRecord::Migration
  def change
    create_table :user_project_companies do |t|
      t.references :user
      t.references :project
      t.references :company

      t.timestamps
    end
    add_index :user_project_companies, :user_id
    add_index :user_project_companies, :project_id
    add_index :user_project_companies, :company_id
  end
end

But do note that you will have to add :id => false and remove t.timestamps if you don't need those.

Another thing is that it will also generate a model named "UserProjectCompanies" and some specs for it.

Upvotes: 1

Prashant4224
Prashant4224

Reputation: 1601

Hey you made typo error referencess, instead use references

 rails g migration CreateJoinTableUserProjectCompany user:references project:references company:references

Upvotes: 0

Related Questions