January 2021
Intermediate
240 pages
5h 32m
Japanese
Content preview from 図解まるわかり データベースのしくみ
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.
164
本のレビューサイトのテーブルを設計
する例③ ～必要なテーブルの決定～
5-18
5-16で整理した要件や、5-17で作成したER図（図 5-30）などの内
容をふまえて、必要なテーブルやカラムを決めるを行ってい
きます。その途中経過が図5-31 のようになりました。
今回の場合はER図とほぼ同様の形でユーザー、レビュー、本を保存す
るテーブルを設けます。ここでもし必要であれば正規化を行い、テーブル
の分離なども検討します。それぞれのテーブルにはレコードを識別するた
めの「id」カラムも設けました。
また、ユーザーとレビューは1 対多の関係になっており、多にあたるレ
ビューのテーブルに、レコードを紐付けるためのカラムとして「ユーザー
ID」を設けておく必要があります。同様にして、本とレビューテーブルを
紐付けるためにレビューテーブルに「本ID」カラムを設けてあります。
図5-30 の他にも必要なテーブルがまだあります。図5-30 で表したER
図では、お気に入り機能のためにユーザーと本は多対多の関係にありまし
た。このような関係をテーブルで表現するために、図5-32 のようにお気
に入りテーブルも追加する必要があります。
ユーザーと本のテーブルの間にお気に入りテーブルを新たに設け、
ことができます。このような役割のテーブルのことを中間テーブルと
呼びます。
これで1 人のユーザーから複数の本、 ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.