TAGS:

ruby  rails  migration  database  join 

Related:

• Adding fields to table via migration.
• Creating migration file using generate migration
• Creation migration file using generate model.
• Creating migration file using scaffold.
• Drop tables using migration.
• Editing migration file manually.</li>
• Seeding data into tables via migration.
• Migration specific VERSION or STEP.
• Removing fields from tables via migration.
• Setting rails environment via migration command.
• Setup, reset and drop database
</ul>


Joining Two Tables Via Rails Migration.

First, We suppose that you have two tables at least. In our example, we have `books` and `authors` tables, so we can join them using migration by adding `references` column which is author's `id` of the `book`. Or in other word, each record in `books` has its author's `id` as:

rails g migration AddAuthorRefToBooks author:references

This will generate a migration file to add this column as:

class AddAuthorRefToBooks < ActiveRecord::Migration
  def change
    add_reference :books, :author, index: true, foreign_key: true
  end
end

Then, Apply changes to database using:

rake db:migrate

Note that you can undo this migration using:

rake db:rollback

Now, You need to manually join these table via `model` by : > >Adding `has_many :books` in the `author` model > >Adding `belongs_to :author` in the `book` model > In `models/author.rb`

has_many :books

In `models/book.rb`

belongs_to :author

Now, Take a look to this tutorial video: