ActiveRecord 使用技巧

gem install mysql2

直接gem install 发生异常，需要先安装mysql开发包，ubuntu下是这样的： sudo apt-get install libmysql-ruby libmysqlclient-dev

脱离rails单独使用ActiveRecord(mysql)

require 'mysql2'
require 'active_record'
$dbconfig = {
   'development' => {
      :adapter  => 'mysql2',
      :username => 'xxx',
      :password => 'xxx',
      :database => 'development',
      :host     => '127.0.0.1',
      :pool     => 10
   },
   'production' => {
      :adapter  => 'mysql2',
      :username => 'xxx',
      :password => 'xxx',
      :database => 'production',
      :host     => '127.0.0.1',
      :pool     => 10

   }
}
ActiveRecord::Base.establish_connection($dbconfig['development'])
class Post < ActiveRecord::Base
end
puts Post.table_name    #posts

定义一个类继承于ActiveRecord::Base

数据库内按照业务逻辑拆表，表内各个字段名一致，表名不同:
beijing_keywords
shanghai_keyowrds
guangzhou_keywords

class Keyword < ActiveRecord::Base
    def self.config(city_name)
        self.table_name = "#{city_name}_keywords"
        self
    end
end
keyword_class = Keyword.config("beijing")
puts keyword_class.table_name   #beijing_keywords
p keyword_class.take            #beijing_keywords first record

ActiveRecord Association

有下面两套表：
beijing_keywords
shanghai_keyowrds
guangzhou_keywords
beijing_adgroups
shanghai_adgroups
guangzhou_adgroups
keyword与adgroup是1-n的关系

class Keyword < ActiveRecord::Base
    belongs_to :adgroup
    def self.config(city_name)
        self.table_name = "#{city_name}_keywords"
        self
    end
end
class Adgroup < ActiveRecord::Base
    has_many :keywords
    def self.config(city_name)
        self.table_name = "#{city_name}_keywords"
        self
    end
end

city_name = "beijing"
keyword_class = Keyword.config(city_name)
adgroup_class = Adgroup.config(city_name)
#根据adgroup的一个字段adgroup_name = "hello"查询keywords
keyword_class.joins(:adgroup).where("#{adgroup_class.table_name}.adgroup_name" => "hello" )
#获取id = 1的keyword对应的adgroup
keyword = keyword_class.find(1)
keyword.adgroup
#获取id = 10的 adgroup 对应的 keywords
adgroup = adgroup_class.find(10)
adgroup.keywords

updated_at 字段自动更新为当前时间

updatedat
updatedon
ruby ActiveRecord::Base.record_timestamps = true #开启自动更新updated_at ActiveRecord::Base.record_timestamps = false #关闭

findbysql 传递参数

Db::Keyword.find_by_sql ["select * from keywords where id > ? and adgroup_id = ?",id,adgroup_id]