初めてのRuby on Rails データベースの確認、操作、表紙(4)

 

初めてのRuby on Rails データベースの確認、操作、表紙(4)

 

1. データベースの確認

 

DatabaseをCommandで操作できるモード

rails dbconsole

 

 テーブルリスト確認

 - コマンドを使用してデータベース内のすべてのテーブルを確認る。

.tables [テーブル名]

 

sqlite> .schema [テーブル名]

コマンドを使用して、特定のテーブルのスキーマを確認。

.schema users

CREATE TABLE IF NOT EXISTS "users" (
"id" integer PRIMARY KEY AUTOINCREMENT NOT NULL, 
"name" varchar, 
"age" integer, 
"created_at" datetime(6) NOT NULL, 
"updated_at" datetime(6) NOT NULL);

 

SQLクエリを使用してデータを確認できる。

select * from users;

 

終了 : .quit. / .q / .exit

 

---

2. データベースの操作

 

rails Consoleを開く

rails c / rails console

 

データを確認する

User.all

 

irb(main):001> User.all
  User Load (0.1ms)  SELECT "users".* FROM "users"
=> []

 

データを作る

User.new　
＃newメソッドは新しいインスタンスをメモリにのみ生成する。 これはデータベースには反映されない。
＃生成されたインスタンスは、後で必要なプロパティを設定した後、saveメソッドを呼び出してデータベースに保存できる。
＃newは、データを保存する前にインスタンスの追加作業や検証が必要なときに便利。

User.create
＃createメソッドはモデルの新しいインスタンスを生成し、そのインスタンスをデータベースにすぐに保存する。
＃createはnewとsaveを合わせたものと同じ作業を1段階で行える。
＃インスタンスの作成と同時に保存が必要なときに便利。

rb(main):002> user = User.new
=> #<User:0x0000000109ef1f78 id: nil, name: nil, age: nil, created_at: nil, updated_at: nil>
irb(main):003> user.name = 'Arang'
=> "Arang"
irb(main):004> user.age = 20
=> 20

 

 newで作れられたインスタンスを保存

user.save

irb(main):005> user.save
  TRANSACTION (0.1ms)  begin transaction
  User Create (1.4ms)  INSERT INTO "users" ("name", "age", "created_at", "updated_at") VALUES (?, ?, ?, ?)  [["name", "Arang"], ["age", 20], ["created_at", "2023-12-31 11:00:05.589577"], ["updated_at", "2023-12-31 11:00:05.589577"]]
  TRANSACTION (1.6ms)  commit transaction
=> true

 

Userを確認する

irb(main):010> User.all
  User Load (0.3ms)  SELECT "users".* FROM "users"
=> 
[#<User:0x0000000109b3dd50
  id: 1,
  name: "Arang",
  age: 20,
  created_at: Sun, 31 Dec 2023 11:00:05.589577000 UTC +00:00,
  updated_at: Sun, 31 Dec 2023 11:00:05.589577000 UTC +00:00>,
 #<User:0x0000000109b3dc10

 

データをUpdateする

user.update

irb(main):015> user
=> 
#<User:0x000000010a974ec8
 id: 1,
 name: "Arang",
 age: 20,
 created_at: Sun, 31 Dec 2023 11:00:05.589577000 UTC +00:00,
 updated_at: Sun, 31 Dec 2023 11:00:05.589577000 UTC +00:00>
irb(main):016> 
irb(main):017> user.update(age: 22)
  TRANSACTION (0.1ms)  begin transaction
  User Update (1.0ms)  UPDATE "users" SET "age" = ?, "updated_at" = ? WHERE "users"."id" = ?  [["age", 22], ["updated_at", "2023-12-31 11:14:55.742065"], ["id", 1]]
  TRANSACTION (1.9ms)  commit transaction
=> true
irb(main):018> user
=> 
#<User:0x000000010a974ec8
 id: 1,
 name: "Arang",
 age: 22,
 created_at: Sun, 31 Dec 2023 11:00:05.589577000 UTC +00:00,
 updated_at: Sun, 31 Dec 2023 11:14:55.742065000 UTC +00:00>

 

データをDeleteする

user.destroy

irb(main):019> user = User.find(2)
  User Load (0.3ms)  SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT ?  [["id", 2], ["LIMIT", 1]]
=> 
#<User:0x000000010a97f288
...
irb(main):020> user
=> 
#<User:0x000000010a97f288
 id: 2,
 name: "hana",
 age: 25,
 created_at: Sun, 31 Dec 2023 11:00:50.010306000 UTC +00:00,
 updated_at: Sun, 31 Dec 2023 11:00:50.010306000 UTC +00:00>
irb(main):021> user.destroy
  TRANSACTION (0.1ms)  begin transaction
  User Destroy (0.9ms)  DELETE FROM "users" WHERE "users"."id" = ?  [["id", 2]]
  TRANSACTION (1.6ms)  commit transaction
=> 
#<User:0x000000010a97f288
 id: 2,
 name: "hana",
 age: 25,
 created_at: Sun, 31 Dec 2023 11:00:50.010306000 UTC +00:00,
 updated_at: Sun, 31 Dec 2023 11:00:50.010306000 UTC +00:00>
irb(main):022> User.all
  User Load (0.4ms)  SELECT "users".* FROM "users"
=> 
[#<User:0x000000010a97b7c8
  id: 1,
  name: "Arang",
  age: 22,
  created_at: Sun, 31 Dec 2023 11:00:05.589577000 UTC +00:00,
  updated_at: Sun, 31 Dec 2023 11:14:55.742065000 UTC +00:00>]

 

 

Rails Console終了

exit / control + d

---

3. データベースの表紙

例題

登録するユーザーデータ

name : ogumon	age : 20	name : metal greymon	age : 40
name : greymon	age : 30	name : wargreymon	age : 50

 

irb(main):002> agumon = User.new(name: "agumon", age: 20)
=> #<User:0x0000000105f32db0 id: nil, name: "agumon", age: 20, created_at: nil, updated_at: nil>
irb(main):003> agumon.save
  TRANSACTION (0.1ms)  begin transaction
  User Create (0.9ms)  INSERT INTO "users" ("name", "age", "created_at", "updated_at") VALUES (?, ?, ?, ?)  [["name", "agumon"], ["age", 20], ["created_at", "2023-12-31 11:29:27.819163"], ["updated_at", "2023-12-31 11:29:27.819163"]]
  TRANSACTION (1.4ms)  commit transaction
=> true

irb(main):004> greymon = User.new(name: "greymon", age: 30)
=> #<User:0x0000000105eb85d8 id: nil, name: "greymon", age: 30, created_at: nil, updated_at: nil>
irb(main):005> greymon.save
  TRANSACTION (0.1ms)  begin transaction
  User Create (1.0ms)  INSERT INTO "users" ("name", "age", "created_at", "updated_at") VALUES (?, ?, ?, ?)  [["name", "greymon"], ["age", 30], ["created_at", "2023-12-31 11:29:52.551931"], ["updated_at", "2023-12-31 11:29:52.551931"]]
  TRANSACTION (1.4ms)  commit transaction
=> true

irb(main):006> metalgreymon = User.new(name: "metalgreymon", age: 40)
=> #<User:0x0000000107318848 id: nil, name: "metalgreymon", age: 40, created_at: nil, updated_at: nil>
irb(main):008> metalgreymon.save
  TRANSACTION (0.1ms)  begin transaction
  User Create (0.8ms)  INSERT INTO "users" ("name", "age", "created_at", "updated_at") VALUES (?, ?, ?, ?)  [["name", "metalgreymon"], ["age", 40], ["created_at", "2023-12-31 11:30:25.943705"], ["updated_at", "2023-12-31 11:30:25.943705"]]
  TRANSACTION (1.4ms)  commit transaction
=> true

irb(main):009> wargreymon = User.new(name: "wargreymon", age: 50)
=> #<User:0x00000001071ba280 id: nil, name: "wargreymon", age: 50, created_at: nil, updated_at: nil>
irb(main):011> wargreymon.save
  TRANSACTION (0.1ms)  begin transaction
  User Create (1.1ms)  INSERT INTO "users" ("name", "age", "created_at", "updated_at") VALUES (?, ?, ?, ?)  [["name", "wargreymon"], ["age", 50], ["created_at", "2023-12-31 11:31:01.477176"], ["updated_at", "2023-12-31 11:31:01.477176"]]
  TRANSACTION (1.4ms)  commit transaction
=> true

 

userscontroller.rb

irb(main):011> wargreymon.save
  TRANSACTION (0.1ms)  begin transaction
  User Create (1.1ms)  INSERT INTO "users" ("name", "age", "created_at", "updated_at") VALUES (?, ?, ?, ?)  [["name", "wargreymon"], ["age", 50], ["created_at", "2023-12-31 11:31:01.477176"], ["updated_at", "2023-12-31 11:31:01.477176"]]
  TRANSACTION (1.4ms)  commit transaction
=> true

 

index.html.erb

<h1>get users Users#index</h1>
<p>Find me in app/views/users/index.html.erb</p>

<h1><%= @hello %><h1>

<p><%= @num %></p>

<ul>
  <% @users.each do |user| %>
    <li>
      <%= user.id %>, <%= user.name %>, <%= user.age %>
    </li>
  <% end %>
</ul>

<% %> : Rubyコードを実行するが、結果を出力しない。 反復文、条件文、変数割り当てなどに使用。
<%=　%> : Ruby コードを実行し、結果をHTML で出力する。 主に変数の値や計算結果をページに表示するときに使用。

 

---

https://github.com/designAR/First_Rails_introduction/tree/rails_console

GitHub - designAR/First_Rails_introduction