ruby-on-rails - Rails 查询内部连接

Question

clients :has_many :project,:roles

我有实施，但它不是一个好的实施..

Answer 1

joins可以使用多个层次，例如Activity属于Carrier Activity.joins(:carrier => {:projects => {:client => :roles}})

将按照以下方式生成 sql

SELECT * from activities
JOIN carriers on activities.carrier_id = carriers.id
JOIN projects on carriers.id = projects.carrier_id
JOIN clients on projects.client_id = clients.id
JOIN roles on roles.client_id = clients.id

您可以在其中添加您的条件。你需要限定你的列名，即使用projects.id而不是仅仅id让你的数据库知道id你想要哪个。

Answer 2

你的解决方案已经足够好了。也许你可以像这样改进它：

clients = Client.joins(:roles).where("roles.name in ('responsible', 'replacement')")
client_ids = clients.map(:&id)
projects = Project.where('id in (?) && start=? && stop=?',client_ids,params[:start_time],params[:end_time])
project_ids = projects.map(:&id)
carriers = Carrier.joins(:projects).where('projects.id in (?) AND carriers.has_clients=1', project_ids)
carrier_ids = carriers.map(&:id)
activities = Activity.joins(:carriers).where('carriers.id in (?)', carrier_ids)