Rails Migration

http://guides.rubyonrails.org/migrations.html

Migrations methods:

• add_column
• add_index
• change_column
• change_table
• create_table
• drop_table
• remove_column
• remove_index
• rename_column

Basic format YYYYMMDDHHMMSS_create_products.rb

Supported types

• :binary
• :boolean
• :date
• :datetime
• :decimal
• :float
• :integer
• :primary_key
• :string
• :text
• :time
• :timestamp especial type:
• :references

create_table

Commands to create migrations

$ rails generate model Product name:string description:text
$ rails generate migration AddPartNumberToProducts part_number:string
$ rails generate migration RemovePartNumberFromProducts part_number:string
$ rails generate migration AddDetailsToProducts part_number:string price:decimal

change_table

• add_column
• add_index
• add_timestamps
• create_table
• remove_timestamps
• rename_column
• rename_index
• rename_table

Running Migrations

$ rake db:migrate VERSION=20080906120000
$ rake db:rollback
$ rake db:rollback STEP=3
$ rake db:migrate:redo STEP=3
$ rake db:reset  #drop database and recreate it
$ rake db:migrate:up VERSION=20080906120000

Migrations commands

rake db:migrate         # Migrate the database (options: VERSION=x, VERBOSE=false).
rake db:migrate:status  # Display status of migrations
rake db:rollback        # Rolls the schema back to the previous version (specify steps w/ STEP=n).
rake db:test:prepare    # Rebuild it from scratch according to the specs defined in the development database

more Database commands (rake -T db)

rake db:create          # Create the database from config/database.yml for the current Rails.env (use db:create:all to create all dbs in t...
rake db:drop            # Drops the database for the current Rails.env (use db:drop:all to drop all databases)
rake db:fixtures:load   # Load fixtures into the current environment's database.
rake db:schema:dump     # Create a db/schema.rb file that can be portably used against any DB supported by AR
rake db:schema:load     # Load a schema.rb file into the database
rake db:seed            # Load the seed data from db/seeds.rb
rake db:setup           # Create the database, load the schema, and initialize with the seed data (use db:reset to also drop the db first)
rake db:structure:dump  # Dump the database structure to db/structure.sql. Specify another file with DB_STRUCTURE=db/my_structure.sql
rake db:version         # Retrieves the current schema version number