Hi friends,

In my last blog  Migrations in Rails: PART 1 - Introduction and Creating Tables I told you what is migration and how we can create tables in migration today I will tell you some other generic queries that are used:

1. Dropping a table:

To drop a table you need to create migrations like:

rails g migration dropArticleTable
#=> 
    invoke  active_record
    create  db/migrate/20160517170025_drop_article_table.rb

Now inside 20160517170025_drop_article_table.rb write this code

    class DropArticleTable < ActiveRecord::Migration
      def change
        drop_table :articles 
      end
      #articles is the name of the table to be dropped
    end

2. Adding a column to a table:

For adding a column to a table you can create migration directly using generator. Suppose you want to add column profile_pic of string type to users table then you can generate it by

rails g migration addProfilePicToUsers profile_pic:string

It will automatically create migration file like:

    class AddProfilePicToUsers < ActiveRecord::Migration
      def change
        add_column :users, :profile_pic, :string
      end
    end

So for adding columns to a table in the end of the migration name you need to specify "ToTableName" and after that column name with their types. It will automatically create migration. You can also edit the migration file before running if you want to add some more thing to this migration

3. Removing a column from a table:

Similarly for removing a column from a table you need to run the migration like:

rails g migration removeProfilePicFromUsers profile_pic:string

It will automatically create migration file like:

    class RemoveProfilePicFromUsers < ActiveRecord::Migration
      def change
        remove_column :users, :profile_pic, :string
      end
    end

Here the default suffix for removing the column is "FromTable" with column names and its type as given in the example above.

Hope you liked this blog.