Ruby on Rails Add a Column After a Specific Column Name

ruby on rails add a column after a specific column name

I doubt it allowed you to actually rake db:migrate this migration, so you shouldn't have to roll back. Just remove the bottom three add_columns and replace the top one with

add_column :patient_allergies, :reaction_id, :integer, after: :patient_id

and it should be fine to migrate. For future reference, here's what that command you entered should look like:

rails generate migration add_reaction_id_to_patient_allergies reaction_id:integer

The space before integer made the generator think it was a new column. Sadly you can't use Ruby syntax (a => b) on the command line either.

Adding a column before another one in Rails

You're able to insert a column at the front of your table by using the :first option:

add_column :table_name, :column_name, :column_type, first: true

You can still use :after to handle all other positioning cases.

Adding a column to an existing table in a Rails migration

If you have already run your original migration (before editing it), then you need to generate a new migration (rails generate migration add_email_to_users email:string will do the trick).
It will create a migration file containing line:
add_column :users, email, string
Then do a rake db:migrate and it'll run the new migration, creating the new column.

If you have not yet run the original migration you can just edit it, like you're trying to do. Your migration code is almost perfect: you just need to remove the add_column line completely (that code is trying to add a column to a table, before the table has been created, and your table creation code has already been updated to include a t.string :email anyway).

PostgreSQL: add_column after option usage in Rails migration

Your last definition is correct. But the problem here isn't with Rails, but with PostgreSQL, which doesn't allow to add a column at specific position. Read more: How can I specify the position for a new column in PostgreSQL?

Adding a new column to model

You are doing it Wrong.

The syntax should be

rails g migration add_column_first_name_to_users first_name:string

rails g migration add_column_last_name_to_users last_name:string

or simply

rails g migration add_first_name_to_users first_name:string
rails g migration add_last_name_to_users last_name:string

or

The best way is to generate them in single Command(@RSB said).

In a Rails Migration (MySQL), can you specify what position a new column should be?

This is now possible in Rails 2.3.6+ by passing the :after parameter

https://rails.lighthouseapp.com/projects/8994/tickets/3286-patch-add-support-for-mysql-column-positioning-to-migrations

To everyone that doesn't see the advantage in having this feature: do you never look at your database outside of the ORM? If I'm viewing in any sort of UI, I like having things like foreign keys, status columns, flags, etc, all grouped together. This doesn't impact the application, but definitely speeds up my ability to review data.

How can I rename a database column in a Ruby on Rails migration?

rename_column :table, :old_column, :new_column

You'll probably want to create a separate migration to do this. (Rename FixColumnName as you will.):

bin/rails generate migration FixColumnName
# creates  db/migrate/xxxxxxxxxx_fix_column_name.rb

Then edit the migration to do your will:

# db/migrate/xxxxxxxxxx_fix_column_name.rb
class FixColumnName < ActiveRecord::Migration
  def self.up
    rename_column :table_name, :old_column, :new_column
  end

  def self.down
    # rename back if you need or do something else or do nothing
  end
end

---

For Rails 3.1 use:

While, the up and down methods still apply, Rails 3.1 receives a change method that "knows how to migrate your database and reverse it when the migration is rolled back without the need to write a separate down method".

See "Active Record Migrations" for more information.

rails g migration FixColumnName

class FixColumnName < ActiveRecord::Migration
  def change
    rename_column :table_name, :old_column, :new_column
  end
end

If you happen to have a whole bunch of columns to rename, or something that would have required repeating the table name over and over again:

rename_column :table_name, :old_column1, :new_column1
rename_column :table_name, :old_column2, :new_column2
...

You could use change_table to keep things a little neater:

class FixColumnNames < ActiveRecord::Migration
  def change
    change_table :table_name do |t|
      t.rename :old_column1, :new_column1
      t.rename :old_column2, :new_column2
      ...
    end
  end
end

Then just db:migrate as usual or however you go about your business.

---

For Rails 4:

While creating a Migration for renaming a column, Rails 4 generates a change method instead of up and down as mentioned in the above section. The generated change method is:

$ > rails g migration ChangeColumnName

which will create a migration file similar to:

class ChangeColumnName < ActiveRecord::Migration
  def change
    rename_column :table_name, :old_column, :new_column
  end
end

Specifying column name in a references migration

Do it manually:

add_column :post, :author_id, :integer

but now, when you create the belongs_to statement, you will have to modify it, so now you have to call

def post
    belongs_to :user, :foreign_key => 'author_id'
end

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