Rails Migration参考

更新到最新版本：
rake db:migrate
重设数据库：
rake db:migrate VERSION=0


字段操作

1、字段类型
:binary, :boolean, :date, :datetime, :float, :integer, :string, :text, :time, :timestamp

2、add_column 添加字段
参数
:null => true or false 是否可为null
:limit => size  字段大小，通常是string字段的长度
:default => value 缺省的值

add_column 
:orders
, 
:placed_at
, 
:datetime
, 
:default
 => 
Time
.now

3、rename_column 字段名修改

class
 RenameEmailColumn < ActiveRecord::Migration
      
def
 
self
.up
            rename_column 
:orders
, 
:e_mail
, 
:customer_email
      
end
     
def
 
self
.down
            rename_column 
:orders
, 
:customer_email
, 
:e_mail
     
end
end

4、change_column  字段类型属性修改

def
 
self
.up
       change_column 
:orders
, 
:order_type
, 
:string
, 
:null
 => 
false
end
def
 
self
.down
       change_column 
:orders
, 
:order_type
, 
:integer
end

表操作

class
 CreateOrderHistories < ActiveRecord::Migration
    
def
 
self
.up
        create_table 
:order_histories
 
do
 
|t
|
              t.column 
:order_id
, 
:integer
, 
:null
 => 
false
              t.column 
:created_at
, 
:timestamp
              t.column 
:notes
, 
:text
         
end
    
end
    
def
 
self
.down
        drop_table 
:order_histories
    
end
end

重命名rename_table

索引

class
 AddCustomerNameIndexToOrders < ActiveRecord::Migration
    
def
 
self
.up
         add_index 
:orders
, 
:name
    
end
    
def
 
self
.down
         remove_index 
:orders
, 
:name
    
end
end

PK

create_table 
:tickets
, 
:primary_key
 => 
:ticket_number
 
do
 
|t
|
    t.column 
:created_at
, 
:timestamp
    t.column 
:description
, 
:text
end

raise ActiveRecord::IrreversibleMigration 不可逆错误

class
 ChangeOrderTypeToString < ActiveRecord::Migration
    
def
 
self
.up
        change_column 
:orders
, 
:order_type
, 
:string
, 
:null
 => 
false
    
end
    
def
 
self
.down
        
raise
 ActiveRecord::IrreversibleMigration
    
end
end