如何使用arel / relational algebra和has_many获取不同的值：through
当我试图显示一个人所在的所有电影，并且他们在电影中有超过1个角色（导演，作家，演员）时，我会为该电影获得多行。如果我添加.select（'DISTINCT id'）或电影。*来尝试消除重复，我会收到以下错误：
Mysql2 ::错误：您的SQL语法有错误;查看与您的MySQL服务器版本对应的手册，以便在'DISTINCT idFROM
movies
movie_people
movies
movie_peop' at line 1: SELECT
.*, DISTINCT id FROM
INNER JOIN
ON
.id =
.movie_id WHERE ((
class PeopleController < ApplicationController
def show
@person = Person.find(params[:id])
@movies = @person.movies.select('DISTINCT id').
paginate :per_page => 18, :page => params[:page],
:order => sort_order(params[:sort])
end
class Person < ActiveRecord::Base
has_many :movie_people
has_many :movies, :through => :movie_people
end
class MoviePerson < ActiveRecord::Base
belongs_to :movie
belongs_to :person
end
class Movie < ActiveRecord::Base
has_many :movie_people
has_many :people, :through => :movie_people
end
create_table "people", :force => true do |t|
t.string "name"
end
create_table "movie_people", :force => true do |t|
t.integer "movie_id"
t.integer "person_id"
t.integer "role"
end
create_table "movies", :force => true do |t|
t.string "title"
t.string "year"
end
Title:<%= @movie.title %><br>
Year:<%= @movie.year %><br>
<% @movie.movie_people.group_by(&:role).each do |r, a| %>
<%= %w(Director: Writer: Cast:)[r] %>
<% a.each do |c| %>
<%= link_to c.person.name,
:controller => 'people', :action => 'show', :id => c.person.id %>
<% end %><br>
<% end %>
Name:<%= @person.name %>
<% @movies.each do |movie| %>
<br><%= link_to movie.title, movie %> (<%= movie.year %>)
<% end %>
没有找到相关结果
已邀请:
3 个回复
豆兢
生成适当的SQL。我不确定如何将Arel添加到has_many关联中，但是在常规（控制器）代码中它会像请参阅http://apidock.com/rails/ActiveRecord/QueryMethods/uniq和Rails Arel选择不同的列瞧叮
@person.movies.except(:select).select('DISTINCT id')替秀宝