Essential Books

Change an existing columns type

suggest change

To modify an existing column in Rails with a migration, run the following command: 

rails g migration change_column_in_table

This will create a new migration file in db/migration directory (if it doesn’t exist already), which will contain the file prefixed with timestamp and migration file name which contains the below content: 

def change
  change_column(:table_name, :column_name, :new_type)
end

Rails Guide – Changing Columns

A longer but safer method

The above code prevents the user from ever rolling back the migration. You can avoid this problem by splitting the change method into separate up and down methods: 

def up
  change_column :my_table, :my_column, :new_type
end

def down
  change_column :my_table, :my_column, :old_type
end
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ActiveRecord migrations:
* ActiveRecord Migrations
* Adding multiple columns to a table
* Add a reference column to a table
* Rollback migrations
* Add a new column with an index
* Run specific migration
* Redo migrations
* Remove an existing column from a table
* Add a new column to a table
* Create a new table
* Running migrations
* Running migrations in different environments
* Add column with default value
* Change an existing columns type
* Create a hstore column
* Add a self reference
* Create a join table
* Create an array column
* Changing Tables
* Checking migration status
* Add an unique column to a table
* Forbid null values
* Adding a NOT NULL constraint to existing data
Table Of Contents
0 Getting started with Ruby on Rails
1 Routing
2 ActiveRecord
3 Views
4 ActiveRecord migrations
5 Rails best practices
6 Naming conventions
7 ActionCable
8 ActiveModel
9 User Authentication in Rails
10 ActiveRecord Associations
11 ActiveRecord validations
12 ActiveRecord Query Interface
13 ActionMailer
14 Rails generate commands
15 Configuration
16 I18N - internalization
17 Using Google Maps with Rails
18 File Uploads
19 Caching
20 ActionController
21 Configuration
22 Safe constantize
23 Rails 5
24 Authorization with CanCan
25 Mongoid
26 Gems
27 Change default timezone
28 Asset pipeline
29 Upgrading Rails
30 ActiveRecord locking
31 Debugging
32 Configure Angular with Rails
33 Rails logger
34 Prawn PDF
35 Rails API
36 Deploying a Rails app on Heroku
37 ActiveSupport
38 Form Helpers
39 ActiveRecord transactions
40 RSpec and Ruby on Rails
41 Decorator pattern
42 Elasticsearch
43 React with Rails
44 Rails cookbook
45 Multi-purpose ActiveRecord columns
46 Class organization
47 Shallow Routing
48 Model states AASM
49 Rails 5 API Authentication
50 Testing Rails Applications
51 Active Jobs
52 Rails frameworks over the years
53 Nested form
54 Factory Girl
55 CSV
56 Tools for code optimization and cleanup
57 ActiveJob
58 Active Model serializers
59 Rails Engine - Modular Rails
60 Single Table inheritance
61 ActiveRecord transactions
62 Turbolinks
63 Friendly ID
64 Securely storing authentications keys
65 Authenticate API using Devise
66 Integrating React.js with Rails using Hyperloop
67 Change a default Rails application environment
68 Reserved words
69 Rails-Engines
70 Adding an Amazon RDS
71 Payment features in Rails
72 Rails on docker
73 Contributors