Rails Migrations #rails #ruby #migrations #activerecord

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##References

• RailsGuides
• ActiveRecord Migrations

##Create Empty Migration command:

rails generate migration MyNewMigration

##Empty Migration Example

  class TenderloveMigration < ActiveRecord::Migration
    def change
      create_table(:horses) do |t|
        t.column :content, :text
        t.column :remind_at, :datetime
      end
    end
  end

##Basic Instructions

• create_table(name, options)
• drop_table(name)
• rename_table(old_name, new_name)
• add_column(table_name, column_name, type, options):
  • types: :string, :text, :integer, :float, :decimal, :datetime, :timestamp, :time, :date, :binary, :boolean.
  • A default value can be specified by passing an options hash like { :default => 11 }. Other options include :limit and :null (e.g. { :limit => 50, :null => false })
• rename_column(table_name, column_name, new_column_name)
• change_column(table_name, column_name, type, options)
• remove_column(table_name, column_names)

##Adding Indexes

• add_index(table_name, column_names, options): Adds a new index with the name of the column. Other options include :name, :unique (e.g. { :name => "users_name_index", :unique => true }) and :order (e.g. { :order => {:name => :desc} })
• remove_index(table_name, :column => column_name)
• remove_index(table_name, :name => index_name)