范围/named_scope 中的多连接查询

Question

是否可以从以下查询中创建 named_scope：

SELECT g.*, b.*
FROM users u 
LEFT JOIN band_users bu ON u.id = bu.uid 
LEFT JOIN bands b ON bu.bid = b.id 
LEFT JOIN bands_gigs bg ON b.id = bg.bid 
LEFT JOIN gigs g ON bg.gid = g.id
WHERE u.id = 1

我正在努力做到这一点，是否可以在 named_scope 或 rails 3 范围内表示多个 :join？

谢谢

Answer 1

是的，可以这样做：

class Band < ActiveRecord::Base
  has_and_belongs_to_many :gigs

  ...
end

class User < ActiveRecord::Base
  has_and_belongs_to_many :bands

  scope :my_scope, joins(:bands => :gigs)
  ...
end