TAGS:

ruby  rails  migration  database  version  step 

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.
• Joining two tables via migration.
• Removing fields from tables via migration.
• Setting rails environment via migration command.
• Setup, reset and drop database
</ul>


How To Migrate Specific VERSION Or STEP In Rails Migration.

First, We suppose that we have three models as:

rails g model author name
rails g model book title brief:text
rails g model admin name

This means that we have three migration files for: > > author migration file. > > book migration file. > > admin migration file. > Each one of these files has its date-time stamps which is its `VERSION`. The `author` migration is `STEP=1`. The `book` migration is `STEP=2`.. The `admin` migration is `STEP=3` If you run `rake db:migrate`, you will migrate all three file in the same sequence, But if you run `rake db:rollback`, you will `rollback` `one by one` in the `opposite` sequence. But if you want to `migrate` or `rollback` specific `STEP` or `VERSION` you can use the following form:

rake db:migrate VERSION=xxxxxxxxxxxxxx
rake db:migrate STEP=x
or
rake db:rollback VERSION=xxxxxxxxxxxxxx
rake db:rollback STEP=x

Where `xxxxxxxxxxxxxx` is the `VERSION` of the desired migration file and `x` is the `index` of the desired migration file. Great Note: You must be care with the `dependencies` between migration file also you may lost you data. Now, Take a look to this tutorial videos: