rails --version
2.3.16
ruby --version
1.8.7
モデル:
class AToB
belongs_to :a
belongs_to :b
default_scope :include => [:a, :b]
end
class A
has_many :a_to_bs
has_many :bs, :through => :a_to_bs
named_scope :twos, :conditions => { :var => 2 }
named_scope :buzzed, :conditions => { :fizz => ['buzz'] }
end
class B
has_many :a_to_bs
has_many :as, :through => :a_to_bs
end
MYSQL クエリ:
SELECT COUNT(DISTINCT a.id), COUNT(DISTINCT c.id)
FROM a_to_b
INNER JOIN a on a.id = a_to_b.a_id
INNER JOIN b on b.id = a_to_b.b_id
WHERE (a.var = 2 AND a.fizz in ('buzz') AND
(b.foo = TRUE OR b.bar = TRUE OR (b.moo = TRUE AND a_to_b.goo = FALSE))
)
このバリエーションも必要になります
SELECT COUNT(DISTINCT a.id), COUNT(DISTINCT c.id)
FROM a_to_b
INNER JOIN a on a.id = a_to_b.a_id
INNER JOIN b on b.id = a_to_b.b_id
WHERE (a.var = 2 AND a.fizz in ('buzz') AND
NOT (b.foo = TRUE OR b.bar = TRUE OR (b.moo = TRUE AND a_to_b.goo = FALSE))
)
私はすでに数え切れないほどの単純な例をグーグルで調べたり、レールのドキュメントを読んだりしましたが、役に立ちませんでした。