Rails deviseを用いたフォロー機能実装時におけるエラー

前提・実現したいこと

Ruby on Railsでユーザー同士のフォロー機能を作っています。
こちらのサイト等を参照しました。
Ruby on Rails ~フォロー（友達申請）機能の実装（コードメモ）

しかし以下のエラーメッセージが発生し、試行錯誤するも先へ進めない状況です。

お見苦しい点がございましたら申し訳ありません。
お知恵を拝借頂けると幸いです。

エラーメッセージ

ActiveRecord::StatementInvalid in Users#show

Showing C:/Users/NEC-PCuser/Dropbox/app/lang_land/app/views/users/_stats.html.erb where line #5 raised:

SQLite3::SQLException: no such column: relationships.following_id: SELECT COUNT(*) FROM "users" INNER JOIN "relationships" ON "users"."id" = "relationships"."following_id" WHERE "relationships"."follower_id" = ?

  <a href="<%= following_user_path(@user) %>">
    <strong id="following" class="stat">
      **<%= @user.followings.count %>**
    </strong>
    フォロー
  </a>

該当のコード(_stats.html.erb)

ruby
1<% @user ||= current_user %>
2<div class="stats">
3  <a href="<%= following_user_path(@user) %>">
4    <strong id="following" class="stat">
5    **<%= @user.followings.count %>**
6    </strong>
7    フォロー
8  </a>
9  &nbsp;
10  <a href="<%= followers_user_path(@user) %>">
11    <strong id="followers" class="stat">
12      <%= @user.followers.count %>
13    </strong>
14    フォロワー
15  </a>
16</div>

該当のコード(show.html.erb)

ruby
1<div class="main user-show">
2  <div class="container">
3    <div class="user">
4      <img src="<%= "/user_images/#{@user.image_name}" %>">
5      <h2><%= @user.name %></h2>
6      <p><%= @user.email %></p>
7      <% if @user.id == @current_user.id %>
8        <%= link_to("編集", "/users/#{@user.id}/edit") %>
9      <% end %>
10    </div>
11    <ul class="user-tabs">
12      <li class="active"><%= link_to("投稿", "/users/#{@user.id}") %></li>
13      <li><%= link_to("いいね!", "/users/#{@user.id}/likes") %></li>
14    </ul>
15    <% @user.posts.each do |post| %>
16      <div class="posts-index-item">
17        <div class="post-left">
18          <img src="<%= "/user_images/#{post.user.image_name}" %>">
19        </div>
20        <div class="post-right">
21          <div class="post-user-name">
22            <%= link_to(post.user.name, "/users/#{post.user.id}") %>
23          </div>
24          <%= link_to(post.title, "/posts/#{post.id}") %>
25        </div>
26      </div>
27    <% end %>
28    <span id="user_<%= @user.id %>" class="follow-wrapper">
29      <%= render 'follow_form', user: @user if signed_in? %>
30    </span>
31    <h4>
32      <%= render 'users/stats' %>
33    </h4>    
34  </div>
35</div>

該当のコード(user.rb)

ruby
1class User < ApplicationRecord
2  # Include default devise modules. Others available are:
3  # :confirmable, :lockable, :timeoutable, :trackable and :omniauthable
4  devise :database_authenticatable, :registerable,
5         :recoverable, :rememberable, :validatable
6  has_secure_password
7
8  validates :name, {presence: true}
9  validates :email, {presence: true, uniqueness: true}
10
11  def posts
12    return Post.where(user_id: self.id)
13  end
14
15  has_many :following_relationships, foreign_key: "follower_id", class_name: "Relationship", dependent: :destroy
16  has_many :followings, through: :following_relationships
17
18  has_many :follower_relationships, foreign_key: "following_id", class_name: "Relationship", dependent: :destroy
19  has_many :followers, through: :follower_relationships
20
21  def following?(other_user)
22    following_relationships.find_by(following_id: other_user.id)
23  end
24
25  def follow!(other_user)
26    following_relationships.create!(following_id: other_user.id)
27  end
28
29  def unfollow!(other_user)
30    following_relationships.find_by(following_id: other_user.id).destroy
31  end
32end

該当のコード(relationship.rb)

ruby
1class Relationship < ApplicationRecord
2  belongs_to :follower, class_name: "User"
3  belongs_to :following, class_name: "User"
4  validates :follower_id, presence: true
5  validates :following_id, presence: true  
6end

該当のコード(migration create_relationships)

ruby
1class CreateRelationships < ActiveRecord::Migration[5.2]
2  def change
3    create_table :relationships do |t|
4      t.integer :follower_id
5      t.integer :followed_id
6
7      t.timestamps
8    end
9    add_index :relationships, :follower_id
10    add_index :relationships, :followed_id
11    add_index :relationships, [:follower_id, :followed_id], unique: true    
12  end
13end