1
我需要使用Rails的Active Record写下面的查询:轨道上选择属性包括表
select c.name,p.name,SUM(e.hours)
from Events e, Projects p, Unities u, Clients c
where e.project_id = p.id AND
p.unity_id = u.id AND
u.client_id = c.id
group by c.name, p.name, e.project_id
型号:
class Event < ActiveRecord::Base
belongs_to :project
class Project < ActiveRecord::Base
belongs_to :unity
has_many :events
end
class Unity < ActiveRecord::Base
belongs_to :client
has_many :projects
end
class Client < ActiveRecord::Base
has_one :unity
end
我有类似:
Event.includes(project: [unity: :client])
但我不知道如何按部分指定属性和组的选择。
我在与你的建议如下因素的输出:#<的ActiveRecord ::关系[#<事件ID:无>,#<事件ID:无> ]>。我如何获得项目名称,客户名称和活动时间的值?谢谢 – 2014-09-23 19:44:35