Adding a column to an existing table in a Rails migration

Question

I have a Users model which needs an  email column  I forgot to add that column during the initial scaffold      I opened the migration file and added t string  email  did rake db migrate  and got a NoMethodError  Then I added the line   add column  users   email   string   again rake db migrate  again NoMethodError   Am I missing a step here   Edit  here s the migration file   class CreateUsers  lt  ActiveRecord  Migration     def self up       add column  users   email   string       create table  users do  t          t string  username         t string  email         t string  crypted password         t string  password salt         t string  persistence token          t timestamps       end     end      def self down       drop table  users     end   end

User · Answer

Use this command at rails console  rails generate migration add fieldname to tablename fieldname string   and   rake db migrate   to run this migration

User · Answer

You could rollback the last migration  by  rake db rollback STEP 1   or rollback this specific migration by  rake db migrate down VERSION  lt YYYYMMDDHHMMSS gt    and edit the file  then run rake db mirgate again

User · Answer

You can also add column to a specific position using before column or after column like   rails generate migration add dob to customer dob date   The migration file will generate the following code except after   email  you need to add after   email or before   email  class AddDobToCustomer  lt  ActiveRecord  Migration 5 2    def change     add column  customers   dob   date  after   email   end end

User · Answer

You can also do this      rails g migration add column to users email string  then rake db migrate   also add  email attribute in your user controller    for more detail check out http   guides rubyonrails org active record migrations html

User · Answer

When I ve done this  rather than fiddling the original migration  I create a new one with just the add column in the up section and a drop column in the down section   You can change the original and rerun it if you migrate down between  but in this case I think that s made a migration that won t work properly   As currently posted  you re adding the column and then creating the table   If you change the order it might work   Or  as you re modifying an existing migration  just add it to the create table instead of doing a separate add column

User · Answer

Sometimes rails generate migration add email to users email string produces a migration like this  class AddEmailToUsers  lt  ActiveRecord  Migration 5 0    def change   end end   In that case you have to manually an add column to change   class AddEmailToUsers  lt  ActiveRecord  Migration 5 0    def change     add column  users   email   string   end end   And then run rake db migrate

User · Answer

You can also force to table columns in table using force  true  if you table is already exist   example   ActiveRecord  Schema define version  20080906171750  do   create table  authors   force  true do  t      t string    name      t datetime  created at      t datetime  updated at    end end

User · Answer

To add a column I just had to follow these steps       rails generate migration add fieldname to tablename fieldname string  Alternative  rails generate migration addFieldnameToTablename  Once the migration is generated  then edit the migration and define all the attributes you want that column added to have   Note  Table names in Rails are always plural  to match DB conventions   Example using one of the steps mentioned previously-   rails generate migration addEmailToUsers rake db migrate   Or    You can change the schema in from db schema rb  Add the columns you want in the SQL query    Run this command  rake db schema load  Warning Note  Bear in mind that  running rake db schema load automatically wipes all data in your tables

User · Answer

You can also do  rake db rollback   if you have not added any data to the tables Then edit the migration file by adding the email column to it and then call   rake db migrate   This will work if you have rails 3 1 onwards installed in your system    Much simpler way of doing it is change let the change in migration file be as it is  use    rake db migrate redo   This will roll back the last migration and migrate it again

User · Answer

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

User · Answer

You also can use special change table method in the migration for adding new columns   change table  users  do  t    t column  email   string end

[ruby-on-rails-3] Adding a column to an existing table in a Rails migration

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