[英]Converting a SQL query to Active Record in Rails 4
這是我的兩個模特
class Comment < ActiveRecord::Base
belongs_to :phone
end
class Phone < ActiveRecord::Base
has_many :comments, :dependent => :destroy
end
這是表的架構
ActiveRecord::Schema.define(version: 20131119231249) do
create_table "comments", force: true do |t|
t.string "username"
t.string "ipaddy"
t.text "pcomments"
t.string "company"
t.string "calltype"
t.datetime "created_at"
t.datetime "updated_at"
t.integer "pnumber"
t.string "source"
end
create_table "phones", force: true do |t|
t.integer "pnumber"
t.text "mrcomment"
t.integer "ccount"
t.datetime "created_at"
t.datetime "updated_at"
end
end
這是有效的原始SQL
SELECT phones.ccount ,
comments.*
FROM phones
INNER JOIN comments
ON phones.pnumber = comments.pnumber;
當我在控制器中運行以下命令時
@phones = Phone.select("phones.ccount, comments.*").joins(:comments).where(:comments => {comments.pnumber => phones.pnumber})
我收到以下錯誤
undefined local variable or method `comments' for #<FrontPageController:0x00000003c56c70>
任何有關活動記錄聲明的幫助都將不勝感激
似乎您錯誤地使用了select()。 您是否閱讀過以下文檔: http : //apidock.com/rails/ActiveRecord/QueryMethods/select ?
來自文檔:“第二個:修改查詢的SELECT語句,以便僅檢索某些字段:”
查詢的語法應更像(使用標准示例):
l = Location.where(["id = ?", id]).select("name, website, city").first.
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