TAGS:

ruby  rails  migration  database 

Related:

• Adding fields to table via 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.
• Joining two 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>


Creating Migration File Via Generating Rails Migration.

The general form is `rails g migration` and then you can create `books` table and state columns names and its datatypes as:

rails g migration CreateBook title:string brief:text

This will create migration file in `db/migrate` folder to create `books` table. Note, The generated file doesn't create `timestamps` fields `created_at` and `updated_at` so, you can add:

t.timestamps null: false

Also, You can edit this file and add or remove columns before making `rake db:migrate` And, You can state all table's columns manually in the migration file not in `rails g migration` command line. Then, Apply changes to database using:

rake db:migrate

Now, You must create `book.rb` model manually in `app/models` to deal with `books` table as:

class Book<ActiveRecord::Base
end

Note that you can undo this migration using:

rake db:rollback

Note, Any `rake db:rollback` may delete stored data in the `targeted` columns and can't be restored again. Also, You can delete the migration file generated by converting `g`(for generate) to `d` (for destroy) in migration command as:

rails g CreateBook title brief:text
#to be
rails d CreateBook title brief:text

The last line will delete the migration file generted by the first line. Now take a look to this tutorial video: