From d82b6f52ba6123a2838c5726c5fa70b33608a2ca Mon Sep 17 00:00:00 2001 From: hachi8833 Date: Sat, 9 Nov 2024 16:15:13 +0900 Subject: [PATCH] =?UTF-8?q?[8.0]=20active=5Frecord=5Fquerying.md=E3=81=AE?= =?UTF-8?q?=E5=8E=9F=E6=96=87=E6=9B=B4=E6=96=B0=E3=82=92=E8=A8=B3=E6=96=87?= =?UTF-8?q?=E3=81=AB=E5=8F=8D=E6=98=A0?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit https://github.com/yasslab/railsguides.jp/issues/1721 --- guides/source/ja/active_record_querying.md | 282 +++++++++++++-------- 1 file changed, 179 insertions(+), 103 deletions(-) diff --git a/guides/source/ja/active_record_querying.md b/guides/source/ja/active_record_querying.md index a453dcf5070..400eb74526b 100644 --- a/guides/source/ja/active_record_querying.md +++ b/guides/source/ja/active_record_querying.md @@ -38,13 +38,13 @@ class Book < ApplicationRecord belongs_to :supplier belongs_to :author has_many :reviews - has_and_belongs_to_many :orders, join_table: 'books_orders' + has_and_belongs_to_many :orders, join_table: "books_orders" scope :in_print, -> { where(out_of_print: false) } scope :out_of_print, -> { where(out_of_print: true) } scope :old, -> { where(year_published: ...50.years.ago.year) } - scope :out_of_print_and_expensive, -> { out_of_print.where('price > 500') } - scope :costs_more_than, ->(amount) { where('price > ?', amount) } + scope :out_of_print_and_expensive, -> { out_of_print.where("price > 500") } + scope :costs_more_than, ->(amount) { where("price > ?", amount) } end ``` @@ -58,7 +58,7 @@ end ```ruby class Order < ApplicationRecord belongs_to :customer - has_and_belongs_to_many :books, join_table: 'books_orders' + has_and_belongs_to_many :books, join_table: "books_orders" enum :status, [:shipped, :being_packed, :complete, :cancelled] @@ -129,35 +129,64 @@ Active Recordでは、データベースからオブジェクトを取り出す * 得られた結果を行ごとに同等のRubyオブジェクトとしてインスタンス化します。 * 指定されていれば、`after_find`を実行し、続いて`after_initialize`コールバックを実行します。 -[`ActiveRecord::Relation`]: https://api.rubyonrails.org/classes/ActiveRecord/Relation.html -[`annotate`]: https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-annotate -[`create_with`]: https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-create_with -[`distinct`]: https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-distinct -[`eager_load`]: https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-eager_load -[`extending`]: https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-extending -[`extract_associated`]: https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-extract_associated -[`find`]: https://api.rubyonrails.org/classes/ActiveRecord/FinderMethods.html#method-i-find -[`from`]: https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-from -[`group`]: https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-group -[`having`]: https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-having -[`includes`]: https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-includes -[`joins`]: https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-joins -[`left_outer_joins`]: https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-left_outer_joins -[`limit`]: https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-limit -[`lock`]: https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-lock -[`none`]: https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-none -[`offset`]: https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-offset -[`optimizer_hints`]: https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-optimizer_hints -[`order`]: https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-order -[`preload`]: https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-preload -[`readonly`]: https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-readonly -[`references`]: https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-references -[`reorder`]: https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-reorder -[`reselect`]: https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-reselect -[`regroup`]: https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-regroup -[`reverse_order`]: https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-reverse_order -[`select`]: https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-select -[`where`]: https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-where +[`ActiveRecord::Relation`]: + https://api.rubyonrails.org/classes/ActiveRecord/Relation.html +[`annotate`]: + https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-annotate +[`create_with`]: + https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-create_with +[`distinct`]: + https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-distinct +[`eager_load`]: + https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-eager_load +[`extending`]: + https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-extending +[`extract_associated`]: + https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-extract_associated +[`find`]: + https://api.rubyonrails.org/classes/ActiveRecord/FinderMethods.html#method-i-find +[`from`]: + https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-from +[`group`]: + https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-group +[`having`]: + https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-having +[`includes`]: + https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-includes +[`joins`]: + https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-joins +[`left_outer_joins`]: + https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-left_outer_joins +[`limit`]: + https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-limit +[`lock`]: + https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-lock +[`none`]: + https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-none +[`offset`]: + https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-offset +[`optimizer_hints`]: + https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-optimizer_hints +[`order`]: + https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-order +[`preload`]: + https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-preload +[`readonly`]: + https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-readonly +[`references`]: + https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-references +[`reorder`]: + https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-reorder +[`reselect`]: + https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-reselect +[`regroup`]: + https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-regroup +[`reverse_order`]: + https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-reverse_order +[`select`]: + https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-select +[`where`]: + https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-where ### 単一のオブジェクトを取り出す @@ -259,8 +288,10 @@ SELECT * FROM customers LIMIT 2 TIP: このメソッドで取り出されるレコードは、利用するデータベースエンジンによって異なることがあります。 -[`take`]: https://api.rubyonrails.org/classes/ActiveRecord/FinderMethods.html#method-i-take -[`take!`]: https://api.rubyonrails.org/classes/ActiveRecord/FinderMethods.html#method-i-take-21 +[`take`]: + https://api.rubyonrails.org/classes/ActiveRecord/FinderMethods.html#method-i-take +[`take!`]: + https://api.rubyonrails.org/classes/ActiveRecord/FinderMethods.html#method-i-take-21 #### `first` @@ -323,8 +354,10 @@ SELECT * FROM customers ORDER BY customers.first_name ASC LIMIT 1 [`first!`][]メソッドの動作は、マッチするレコードが見つからない場合に`ActiveRecord::RecordNotFound`例外が発生する点を除いて、`first`メソッドとまったく同じです。 -[`first`]: https://api.rubyonrails.org/classes/ActiveRecord/FinderMethods.html#method-i-first -[`first!`]: https://api.rubyonrails.org/classes/ActiveRecord/FinderMethods.html#method-i-first-21 +[`first`]: + https://api.rubyonrails.org/classes/ActiveRecord/FinderMethods.html#method-i-first +[`first!`]: + https://api.rubyonrails.org/classes/ActiveRecord/FinderMethods.html#method-i-first-21 #### `last` @@ -387,8 +420,10 @@ SELECT * FROM customers ORDER BY customers.first_name DESC LIMIT 1 [`last!`][]メソッドの動作は、マッチするレコードが見つからない場合に`ActiveRecord::RecordNotFound`例外が発生する点を除いて、`last`メソッドとまったく同じです。 -[`last`]: https://api.rubyonrails.org/classes/ActiveRecord/FinderMethods.html#method-i-last -[`last!`]: https://api.rubyonrails.org/classes/ActiveRecord/FinderMethods.html#method-i-last-21 +[`last`]: + https://api.rubyonrails.org/classes/ActiveRecord/FinderMethods.html#method-i-last +[`last!`]: + https://api.rubyonrails.org/classes/ActiveRecord/FinderMethods.html#method-i-last-21 #### `find_by` @@ -405,7 +440,7 @@ irb> Customer.find_by first_name: 'Jon' 上の文は以下のように書くこともできます。 ```ruby -Customer.where(first_name: 'Lifo').take +Customer.where(first_name: "Lifo").take ``` 上と同等のSQLは以下のようになります。 @@ -426,11 +461,13 @@ irb> Customer.find_by! first_name: 'does not exist' 上の文は以下のように書くこともできます。 ```ruby -Customer.where(first_name: 'does not exist').take! +Customer.where(first_name: "does not exist").take! ``` -[`find_by`]: https://api.rubyonrails.org/classes/ActiveRecord/FinderMethods.html#method-i-find_by -[`find_by!`]: https://api.rubyonrails.org/classes/ActiveRecord/FinderMethods.html#method-i-find_by-21 +[`find_by`]: + https://api.rubyonrails.org/classes/ActiveRecord/FinderMethods.html#method-i-find_by +[`find_by!`]: + https://api.rubyonrails.org/classes/ActiveRecord/FinderMethods.html#method-i-find_by-21 ##### 条件を`id`で指定する @@ -456,7 +493,8 @@ irb> Customer.find_by(id: customer.id_value) # Customer.find_by(id: 10) => # ``` -[`id_value`]: https://api.rubyonrails.org/classes/ActiveRecord/ModelSchema.html#method-i-id_value +[`id_value`]: + https://api.rubyonrails.org/classes/ActiveRecord/ModelSchema.html#method-i-id_value ### 複数のオブジェクトをバッチで取り出す @@ -501,8 +539,10 @@ end レシーバー側に順序がある場合、[`config.active_record.error_on_ignored_order`][]フラグの状態によって振る舞いが変わります。たとえば`true`の場合は`ArgumentError`が発生し、`false`の場合は順序が無視されて警告が発生します。デフォルトは`false`です。このフラグを上書きしたい場合は`:error_on_ignore`オプション（後述）を使います。 -[`config.active_record.error_on_ignored_order`]: configuring.html#config-active-record-error-on-ignored-order -[`find_each`]: https://api.rubyonrails.org/classes/ActiveRecord/Batches.html#method-i-find_each +[`config.active_record.error_on_ignored_order`]: + configuring.html#config-active-record-error-on-ignored-order +[`find_each`]: + https://api.rubyonrails.org/classes/ActiveRecord/Batches.html#method-i-find_each ##### `find_each`のオプション @@ -578,7 +618,8 @@ end ただしこれは順序指定がない場合に限ります。`find_in_batches`メソッドでイテレートするには内部で順序を強制する必要があるためです。 -[`find_in_batches`]: https://api.rubyonrails.org/classes/ActiveRecord/Batches.html#method-i-find_in_batches +[`find_in_batches`]: + https://api.rubyonrails.org/classes/ActiveRecord/Batches.html#method-i-find_in_batches ##### `find_in_batches`のオプション @@ -691,7 +732,8 @@ Book.where("title LIKE ?", Book.sanitize_sql_like(params[:title]) + "%") ``` -[`sanitize_sql_like`]: https://api.rubyonrails.org/classes/ActiveRecord/Sanitization/ClassMethods.html#method-i-sanitize_sql_like +[`sanitize_sql_like`]: + https://api.rubyonrails.org/classes/ActiveRecord/Sanitization/ClassMethods.html#method-i-sanitize_sql_like ### 条件でハッシュを使う @@ -714,7 +756,7 @@ SELECT * FROM books WHERE (books.out_of_print = 1) フィールド名は文字列形式にもできます。 ```ruby -Book.where('out_of_print' => true) +Book.where("out_of_print" => true) ``` belongs_toリレーションシップの場合、Active Recordオブジェクトが値として使われていれば、モデルを指定する時に関連付けキーを利用できます。この方法はポリモーフィックリレーションシップでも同様に利用できます。 @@ -807,28 +849,30 @@ Customer.where.not(nullable_country: nil) # => [#] ``` -[`where.not`]: https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods/WhereChain.html#method-i-not +[`where.not`]: + https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods/WhereChain.html#method-i-not ### OR条件 ２つのリレーションをまたいで`OR`条件を使いたい場合は、１つ目のリレーションで[`or`][]メソッドを呼び出し、そのメソッドの引数に２つ目のリレーションを渡すことで実現できます。 ```ruby -Customer.where(last_name: 'Smith').or(Customer.where(orders_count: [1, 3, 5])) +Customer.where(last_name: "Smith").or(Customer.where(orders_count: [1, 3, 5])) ``` ```sql SELECT * FROM customers WHERE (customers.last_name = 'Smith' OR customers.orders_count IN (1, 3, 5)) ``` -[`or`]: https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-or +[`or`]: + https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-or ### AND条件 `AND`条件は、`where`条件をチェインすることで構成できます。 ```ruby -Customer.where(last_name: 'Smith').where(orders_count: [1, 3, 5])) +Customer.where(last_name: "Smith").where(orders_count: [1, 3, 5]) ``` ```sql @@ -845,7 +889,8 @@ Customer.where(id: [1, 2]).and(Customer.where(id: [2, 3])) SELECT * FROM customers WHERE (customers.id IN (1, 2) AND customers.id IN (2, 3)) ``` -[`and`]: https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-and +[`and`]: + https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-and 並び順 -------- @@ -896,7 +941,7 @@ irb> Book.order("title ASC").order("created_at DESC") ```ruby Book.includes(:author).order(books: { print_year: :desc }, authors: { name: :asc }) # または -Book.includes(:author).order('books.print_year desc', 'authors.name asc') +Book.includes(:author).order("books.print_year desc", "authors.name asc") ``` WARNING: 多くのデータベースシステムでは、`select`、`pluck`、`ids`メソッドを使ってフィールドを選択しています。これらのデータベースシステムでは、選択しているリストに`order`句を使ったフィールドが含まれていないと、`order`メソッドで`ActiveRecord::StatementInvalid`例外が発生します。結果から特定のフィールドを取り出す方法については、次のセクションを参照してください。 @@ -1019,7 +1064,8 @@ FROM orders GROUP BY status ``` -[`count`]: https://api.rubyonrails.org/classes/ActiveRecord/Calculations.html#method-i-count +[`count`]: + https://api.rubyonrails.org/classes/ActiveRecord/Calculations.html#method-i-count HAVING条件 ------ @@ -1085,18 +1131,19 @@ Book.where(id: 10, out_of_print: false).unscope(where: :id) `unscope`をリレーションに適用すると、それにマージされるすべてのリレーションにも影響します。 ```ruby -Book.order('id desc').merge(Book.unscope(:order)) +Book.order("id desc").merge(Book.unscope(:order)) # SELECT books.* FROM books ``` -[`unscope`]: https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-unscope +[`unscope`]: + https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-unscope ### `only` 以下のように[`only`][]メソッドを使って条件を上書きできます。 ```ruby -Book.where('id > 10').limit(20).order('id desc').only(:order, :where) +Book.where("id > 10").limit(20).order("id desc").only(:order, :where) ``` 上で実行されるSQLは以下のようになります。 @@ -1108,7 +1155,8 @@ SELECT * FROM books WHERE id > 10 ORDER BY id DESC SELECT * FROM books WHERE id > 10 ORDER BY id DESC LIMIT 20 ``` -[`only`]: https://api.rubyonrails.org/classes/ActiveRecord/SpawnMethods.html#method-i-only +[`only`]: + https://api.rubyonrails.org/classes/ActiveRecord/SpawnMethods.html#method-i-only ### `reselect` @@ -1162,7 +1210,7 @@ SELECT * FROM books WHERE author_id = 10 ORDER BY year_published DESC `reorder`を使うと、以下のようにbooksで別の並び順を指定できます。 ```ruby -Author.find(10).books.reorder('year_published ASC') +Author.find(10).books.reorder("year_published ASC") ``` 上で実行されるSQLは以下のようになります。 @@ -1226,7 +1274,8 @@ Book.where(out_of_print: true).where(out_of_print: false) SELECT * FROM books WHERE out_of_print = 1 AND out_of_print = 0 ``` -[`rewhere`]: https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-rewhere +[`rewhere`]: + https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-rewhere ### `regroup` @@ -1255,7 +1304,8 @@ Book.group(:author).group(:id) SELECT * FROM books GROUP BY author, id ``` -[`regroup`]: https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-regroup +[`regroup`]: + https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-regroup Nullリレーション ------------- @@ -1347,7 +1397,7 @@ end ```ruby Book.transaction do book = Book.lock.first - book.title = 'Algorithms, second edition' + book.title = "Algorithms, second edition" book.save! end ``` @@ -1484,7 +1534,7 @@ INNER JOIN suppliers ON suppliers.id = books.supplier_id ```ruby time_range = (Time.now.midnight - 1.day)..Time.now.midnight -Customer.joins(:orders).where('orders.created_at' => time_range).distinct +Customer.joins(:orders).where("orders.created_at" => time_range).distinct ``` 上は、`created_at`をSQLの`BETWEEN`式で比較することで、昨日注文を行ったすべての顧客を検索できます。 @@ -1522,7 +1572,7 @@ Customer.joins(:orders).merge(Order.created_in_time_range(time_range)).distinct 関連レコードがあるかどうかにかかわらずレコードのセットを取得したい場合は、[`left_outer_joins`][] メソッドを使います。 ```ruby -Customer.left_outer_joins(:reviews).distinct.select('customers.*, COUNT(reviews.*) AS reviews_count').group('customers.id') +Customer.left_outer_joins(:reviews).distinct.select("customers.*, COUNT(reviews.*) AS reviews_count").group("customers.id") ``` 上のコードは、以下のクエリを生成します。 @@ -1731,9 +1781,12 @@ user.comments.to_a # ActiveRecord::StrictLoadingViolationErrorが発生 ロガーに違反を送信するには、[`config.active_record.action_on_strict_loading_violation`][]を`:log`に変更します。 -[`strict_loading`]: https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-strict_loading -[`config.active_record.strict_loading_by_default`]: configuring.html#config-active-record-strict-loading-by-default -[`config.active_record.action_on_strict_loading_violation`]: configuring.html#config-active-record-action-on-strict-loading-violation +[`strict_loading`]: + https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-strict_loading +[`config.active_record.strict_loading_by_default`]: + configuring.html#config-active-record-strict-loading-by-default +[`config.active_record.action_on_strict_loading_violation`]: + configuring.html#config-active-record-action-on-strict-loading-violation ### `strict_loading!` @@ -1756,7 +1809,8 @@ user.comments.to_a # => [# Book.new => # ``` -[`default_scope`]: https://edgeapi.rubyonrails.org/classes/ActiveRecord/Scoping/Default/ClassMethods.html#method-i-default_scope +[`default_scope`]: + https://edgeapi.rubyonrails.org/classes/ActiveRecord/Scoping/Default/ClassMethods.html#method-i-default_scope ### スコープのマージ @@ -1980,7 +2036,8 @@ SELECT books.* FROM books WHERE (year_published >= 1969) AND (price > 50) 上の例でわかるように、`default_scope`の条件は、`scope`と`where`の条件よりも前に配置されています。 -[`merge`]: https://api.rubyonrails.org/classes/ActiveRecord/SpawnMethods.html#method-i-merge +[`merge`]: + https://api.rubyonrails.org/classes/ActiveRecord/SpawnMethods.html#method-i-merge ### すべてのスコープを削除する @@ -2007,7 +2064,8 @@ irb> Book.unscoped { Book.out_of_print } SELECT books.* FROM books WHERE books.out_of_print = true ``` -[`unscoped`]: https://api.rubyonrails.org/classes/ActiveRecord/Scoping/Default/ClassMethods.html#method-i-unscoped +[`unscoped`]: + https://api.rubyonrails.org/classes/ActiveRecord/Scoping/Default/ClassMethods.html#method-i-unscoped 動的検索 --------------- @@ -2067,7 +2125,8 @@ UPDATE "orders" SET "status" = ?, "updated_at" = ? WHERE "orders"."id" = ? [["s enumの完全なドキュメントについては[`ActiveRecord::Enum`](https://api.rubyonrails.org/classes/ActiveRecord/Enum.html)を参照してください。 -[`enum`]: https://api.rubyonrails.org/classes/ActiveRecord/Enum.html#method-i-enum +[`enum`]: + https://api.rubyonrails.org/classes/ActiveRecord/Enum.html#method-i-enum メソッドチェインを理解する --------------------------------- @@ -2082,9 +2141,9 @@ Active Record パターンには [メソッドチェイン (Method chaining - Wi ```ruby Customer - .select('customers.id, customers.last_name, reviews.body') + .select("customers.id, customers.last_name, reviews.body") .joins(:reviews) - .where('reviews.created_at > ?', 1.week.ago) + .where("reviews.created_at > ?", 1.week.ago) ``` 上のコードから以下のようなSQLが生成されます。 @@ -2101,9 +2160,9 @@ WHERE (reviews.created_at > '2019-01-08') ```ruby Book - .select('books.id, books.title, authors.first_name') + .select("books.id, books.title, authors.first_name") .joins(:author) - .find_by(title: 'Abstraction and Specification in Program Development') + .find_by(title: "Abstraction and Specification in Program Development") ``` 上のコードから以下のようなSQLが生成されます。 @@ -2153,20 +2212,21 @@ COMMIT これは2とおりの方法で実装できます。1つ目は`create_with`を使う方法です。 ```ruby -Customer.create_with(locked: false).find_or_create_by(first_name: 'Andy') +Customer.create_with(locked: false).find_or_create_by(first_name: "Andy") ``` 2つ目はブロックを使う方法です。 ```ruby -Customer.find_or_create_by(first_name: 'Andy') do |c| +Customer.find_or_create_by(first_name: "Andy") do |c| c.locked = false end ``` このブロックは、顧客が作成されるときにだけ実行されます。このコードを再度実行すると、このブロックは実行されません。 -[`find_or_create_by`]: https://api.rubyonrails.org/classes/ActiveRecord/Relation.html#method-i-find_or_create_by +[`find_or_create_by`]: + https://api.rubyonrails.org/classes/ActiveRecord/Relation.html#method-i-find_or_create_by ### `find_or_create_by!` @@ -2183,7 +2243,8 @@ irb> Customer.find_or_create_by!(first_name: 'Andy') ActiveRecord::RecordInvalid: Validation failed: Orders count can't be blank ``` -[`find_or_create_by!`]: https://api.rubyonrails.org/classes/ActiveRecord/Relation.html#method-i-find_or_create_by-21 +[`find_or_create_by!`]: + https://api.rubyonrails.org/classes/ActiveRecord/Relation.html#method-i-find_or_create_by-21 ### `find_or_initialize_by` @@ -2213,7 +2274,8 @@ irb> nina.save => true ``` -[`find_or_initialize_by`]: https://api.rubyonrails.org/classes/ActiveRecord/Relation.html#method-i-find_or_initialize_by +[`find_or_initialize_by`]: + https://api.rubyonrails.org/classes/ActiveRecord/Relation.html#method-i-find_or_initialize_by SQLで検索する -------------- @@ -2227,18 +2289,20 @@ irb> Customer.find_by_sql("SELECT * FROM customers INNER JOIN orders ON customer `find_by_sql`は、カスタマイズしたデータベース呼び出しを簡単な方法で提供し、インスタンス化されたオブジェクトを返します。 -[`find_by_sql`]: https://edgeapi.rubyonrails.org/classes/ActiveRecord/Querying.html#method-i-find_by_sql +[`find_by_sql`]: + https://edgeapi.rubyonrails.org/classes/ActiveRecord/Querying.html#method-i-find_by_sql ### `select_all` -`find_by_sql`は[`connection.select_all`][]と深い関係があります。`select_all`は`find_by_sql`と同様、カスタムSQLを用いてデータベースからオブジェクトを取り出しますが、取り出したオブジェクトをインスタンス化しない点が異なります。このメソッドは`ActiveRecord::Result`クラスのインスタンスを1つ返します。このオブジェクトで`to_a`を呼ぶと、各レコードに対応するハッシュを含む配列を1つ返します。 +`find_by_sql`は[`lease_connection.select_all`][]と深い関係があります。`select_all`は`find_by_sql`と同様、カスタムSQLを用いてデータベースからオブジェクトを取り出しますが、取り出したオブジェクトをインスタンス化しない点が異なります。このメソッドは`ActiveRecord::Result`クラスのインスタンスを1つ返します。このオブジェクトで`to_a`を呼ぶと、各レコードに対応するハッシュを含む配列を1つ返します。 ```irb -irb> Customer.connection.select_all("SELECT first_name, created_at FROM customers WHERE id = '1'").to_a +irb> Customer.lease_connection.select_all("SELECT first_name, created_at FROM customers WHERE id = '1'").to_a => [{"first_name"=>"Rafael", "created_at"=>"2012-11-10 23:23:45.281189"}, {"first_name"=>"Eileen", "created_at"=>"2013-12-09 11:22:35.221282"}] ``` -[`connection.select_all`]: https://api.rubyonrails.org/classes/ActiveRecord/ConnectionAdapters/DatabaseStatements.html#method-i-select_all +[`lease_connection.select_all`]: + https://api.rubyonrails.org/classes/ActiveRecord/ConnectionAdapters/DatabaseStatements.html#method-i-select_all ### `pluck` @@ -2324,7 +2388,8 @@ SELECT "customers"."id" FROM "customers" LEFT OUTER JOIN "reviews" ON "reviews". irb> assoc.unscope(:includes).pluck(:id) ``` -[`pluck`]: https://api.rubyonrails.org/classes/ActiveRecord/Calculations.html#method-i-pluck +[`pluck`]: + https://api.rubyonrails.org/classes/ActiveRecord/Calculations.html#method-i-pluck ### `pick` @@ -2344,7 +2409,8 @@ Customer.where(id: 1).pluck(:id).first Customer.where(id: 1).pick(:id) ``` -[`pick`]: https://api.rubyonrails.org/classes/ActiveRecord/Calculations.html#method-i-pick +[`pick`]: + https://api.rubyonrails.org/classes/ActiveRecord/Calculations.html#method-i-pick ### `ids` @@ -2366,7 +2432,8 @@ irb> Customer.ids SELECT customer_id FROM customers ``` -[`ids`]: https://api.rubyonrails.org/classes/ActiveRecord/Calculations.html#method-i-ids +[`ids`]: + https://api.rubyonrails.org/classes/ActiveRecord/Calculations.html#method-i-ids オブジェクトの存在チェック -------------------- @@ -2382,16 +2449,16 @@ Customer.exists?(1) ```ruby Customer.exists?(id: [1, 2, 3]) # または -Customer.exists?(first_name: ['Jane', 'Sergei']) +Customer.exists?(first_name: ["Jane", "Sergei"]) ``` `exists?`メソッドは、引数なしでモデルやリレーションに使うことも可能です。 ```ruby -Customer.where(first_name: 'Ryan').exists? +Customer.where(first_name: "Ryan").exists? ``` -上の例では、`first_name`が'Ryan'のクライアントが1人でもいれば`true`を返し、それ以外の場合は`false`を返します。 +上の例では、`first_name`が'Ryan'であるクライアントが1人でもいれば`true`を返し、それ以外の場合は`false`を返します。 ```ruby Customer.exists? @@ -2423,7 +2490,8 @@ Customer.first.orders.any? Customer.first.orders.many? ``` -[`exists?`]: https://api.rubyonrails.org/classes/ActiveRecord/FinderMethods.html#method-i-exists-3F +[`exists?`]: + https://api.rubyonrails.org/classes/ActiveRecord/FinderMethods.html#method-i-exists-3F 計算 ------------ @@ -2476,7 +2544,8 @@ Order.average("subtotal") オプションについては、1つ上の[計算](#計算)セクションを参照してください。 -[`average`]: https://api.rubyonrails.org/classes/ActiveRecord/Calculations.html#method-i-average +[`average`]: + https://api.rubyonrails.org/classes/ActiveRecord/Calculations.html#method-i-average ### `minimum` @@ -2488,7 +2557,8 @@ Order.minimum("subtotal") オプションについては、1つ上の[計算](#計算)セクションを参照してください。 -[`minimum`]: https://api.rubyonrails.org/classes/ActiveRecord/Calculations.html#method-i-minimum +[`minimum`]: + https://api.rubyonrails.org/classes/ActiveRecord/Calculations.html#method-i-minimum ### `maximum` @@ -2500,7 +2570,8 @@ Order.maximum("subtotal") オプションについては、1つ上の[計算](#計算)セクションを参照してください。 -[`maximum`]: https://api.rubyonrails.org/classes/ActiveRecord/Calculations.html#method-i-maximum +[`maximum`]: + https://api.rubyonrails.org/classes/ActiveRecord/Calculations.html#method-i-maximum ### `sum` @@ -2512,7 +2583,8 @@ Order.sum("subtotal") オプションについては、1つ上の[計算](#計算)セクションを参照してください。 -[`sum`]: https://api.rubyonrails.org/classes/ActiveRecord/Calculations.html#method-i-sum +[`sum`]: + https://api.rubyonrails.org/classes/ActiveRecord/Calculations.html#method-i-sum EXPLAINを実行する --------------- @@ -2611,7 +2683,8 @@ PostgreSQLの場合は以下のような結果を生成します。 (2 rows) ``` -[`explain`]: https://api.rubyonrails.org/classes/ActiveRecord/Relation.html#method-i-explain +[`explain`]: + https://api.rubyonrails.org/classes/ActiveRecord/Relation.html#method-i-explain ### Explainのオプション @@ -2668,9 +2741,12 @@ NOTE: EXPLAINやANALYZEのオプションは、MySQLやMariaDBのバージョン - [MySQL 8.0][MySQL8-explain] - [MariaDB][MariaDB-explain] -[MySQL5.7-explain]: https://dev.mysql.com/doc/refman/5.7/en/explain.html -[MySQL8-explain]: https://dev.mysql.com/doc/refman/8.0/en/explain.html -[MariaDB-explain]: https://mariadb.com/kb/en/analyze-and-explain-statements/ +[MySQL5.7-explain]: + https://dev.mysql.com/doc/refman/5.7/en/explain.html +[MySQL8-explain]: + https://dev.mysql.com/doc/refman/8.0/en/explain.html +[MariaDB-explain]: + https://mariadb.com/kb/en/analyze-and-explain-statements/ ### EXPLAINの出力結果を解釈する