條件對連接的表 - Rails的

Question

我的模型：

class Review < ActiveRecord::Base 
    belongs_to :business 

class Business < ActiveRecord::Base 
    has_many :reviews 
    has_and_belongs_to_many :categories 

我想在一定類別企業評論：

Review.joins(:business => :categories).where(:business => {:categories => [1,2,3,4]}) 

結果查詢：

SELECT "reviews".* FROM "reviews" INNER JOIN 
"businesses" ON "businesses"."id" = "reviews"."business_id" INNER JOIN 
"businesses_categories" ON "businesses_categories"."business_id" = "businesses"."id" 
INNER JOIN "categories" ON "categories"."id" = "businesses_categories"."category_id" 
WHERE "business"."categories" IN (1, 2, 3, 4) 

但是，我收到以下錯誤：

ActiveRecord::StatementInvalid: PG::Error: ERROR: missing FROM-clause entry 
for table "business" 
LINE 1: ...id" = "businesses_categories"."category_id" WHERE "business"... 

Answer 1

使用此：

Review.joins(:business => :categories).where(:categories => { :id => [1,2,3,4] })