cheat sheets.

--- migrations version 8	Tue Dec 20 11:36:16 -0800 2011
+++ migrations version 13	Sun May 06 12:09:00 -0700 2012
@@ -1,109 +1,117 @@
 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}
+      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
-: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
-:integer	int		int(11)		integer		number(38)
-: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      | db2          | mysql        | openbase     | Oracle        |
+---        | ---          | ---          | ---          | ---           |
+: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        |
+:integer   | int          | int(11)      | integer      | number(38)    |
+: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
-: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)
-:integer	integer		integer		int		int
-:string	*		varchar(255)	varchar(255)	varchar(255)
-:text		text		text		text		text
-:time		time		datetime	datetime	time
-:timestamp	timestamp	datetime	datetime	timestamp
+Rails      | postgresql   | sqlite       | sqlserver    | Sybase        |
+---        | ---          | ---          | ---          | ---           |
+: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)      |
+:integer   | integer      | integer      | int          | int           |
+:string    | *            | varchar(255) | varchar(255) | varchar(255)  |
+:text      | text         | text         | text         | text          |
+:time      | time         | datetime     | datetime     | time          |
+:timestamp | timestamp    | datetime     | datetime     | timestamp     |