cheat sheets.

--- migrations version 4	Sat May 15 03:03:52 -0700 2010
+++ migrations version 8	Tue Dec 20 11:36:16 -0800 2011
@@ -1,118 +1,109 @@
 Methods:
   create_table(name, options)
   drop_table(name)
   rename_table(old_name, new_name)
   add_column(table_name, column_name, type, options)
   rename_column(table_name, column_name, new_column_name)
   change_column(table_name, column_name, type, options)
   remove_column(table_name, column_name)
   add_index(table_name, column_name, index_type)
   remove_index(table_name, column_name)
   change_table(table_name) {|Table.new(table_name, self)| ...} 
+  change_column_default(table_name, column_name, default)
+  change_column_null(table_name, column_name, null, default = nil)
 
 Available Column Types (mappings are below):
   * integer
   * float
   * datetime
   * date
   * timestamp
   * time
   * text
   * string
   * binary
   * boolean
   * decimal :precision, :scale
 
 Valid Column Options:
   * limit
   * null (i.e. ":null => false" implies NOT NULL)
   * default (to specify default values)
   * :decimal, :precision => 8, :scale => 3
 
 Rake Tasks:
   rake db:schema:dump: run after you create a model to capture the schema.rb
   rake db:schema:import: import the schema file into the current database (on
   error, check if your schema.rb has ":force => true" on the create table
   statements
   ./script/generate migration MigrationName: generate a new migration with a new
   'highest' version (run './script/generate migration' for this info at your
   fingertips)
   rake db:migrate: migrate your current database to the most recent version
   rake db:migrate VERSION=5: migrate your current database to a specific version
   (in this case, version 5)
   rake db:rollback: migrate down one migration
   rake db:rollback STEP=3: migrate down three migrations
   rake db:migrate RAILS_ENV=production: migrate your production database
 
 SQL:
   Queries can be executed directly:
   execute 'ALTER TABLE researchers ADD CONSTRAINT fk_researchers_departments
   FOREIGN KEY ( department_id ) REFERENCES departments( id )'
 
 Example Migration:
   class UpdateUsersAndCreateProducts < ActiveRecord::Migration
     def self.up
       rename_column "users", "password", "hashed_password" 
       remove_column "users", "email" 
 
        User.reset_column_information
        User.find(:all).each{|u| #do something with u}
 
-      create_table &quot;products&quot;, :force =&gt; true do |t|
-          t.column &quot;name&quot;, :text
-          t.column &quot;description&quot;, :text
-          t.column &quot;price&quot;, :decimal, :precision =&gt; 9, :scale =&gt; 2
-          t.column &quot;category_id&quot;, :integer
-      end
-
-      #the rails 2.0 way:
       create_table :people do |t|
         t.integer :account_id
         t.string  :first_name, :last_name, :null => false
         t.text    :description
         t.references :category # is the equivalent of t.integer :category_id
         t.timestamps
       end
     end
 
     def self.down
       rename_column "users", "hashed_password", "password" 
       add_column "users", "email", :string
       drop_table "products" 
     end
   end
 
 Find Highest version:
   script/runner "puts ActiveRecord::Migrator.current_version"
 
 Database Mapping
 
 Rails		db2		mysql		openbase	Oracle
-:binary		blob(32678)	blob		object		blob
+:binary	blob(32678)	blob		object		blob
 :boolean	decimal(1)	tinyint(1)	boolean		number(10)
 :date		date		date		date		date
 :datetime	timestamp	datetime	datetime	date
 :decimal	decimal		decimal		decimal		decimal
-:float		float		float		float		number
+:float	float		float		float		number
 :integer	int		int(11)		integer		number(38)
-:string		varchar(255)	varchar(255)	char(4096)	varchar2(255)
+:string	varchar(255)	varchar(255)	char(4096)	varchar2(255)
 :text		clob(32768)	text		text		clob
 :time		time		time		time		date
 :timestamp	timestamp	datetime	timestamp	date
 
 Rails		postgresql	sqlite		sqlserver	Sybase
-:binary		bytea		blob		image		image
+:binary	bytea		blob		image		image
 :boolean	boolean		boolean		bit		bit
 :date		date		date		datetime	datetime
 :datetime	timestamp	datetime	datetime	datetime
 :decimal	decimal		decimal		decimal		decimal
-:float		float		float		float(8)	float(8)
+:float	float		float		float(8)	float(8)
 :integer	integer		integer		int		int
-:string		*		varchar(255)	varchar(255)	varchar(255)
+:string	*		varchar(255)	varchar(255)	varchar(255)
 :text		text		text		text		text
 :time		time		datetime	datetime	time
 :timestamp	timestamp	datetime	datetime	timestamp
-
-
-