多在范围/ named_scope连接查询

Question

是否有可能从下列查询创建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 

我努力做到这一点，是有可能代表多：在named_scope或导轨联接3范围？

感谢

Answer 1

是的，这是可以做到的：

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