August 2024
Intermediate to advanced
392 pages
10h 4m
Japanese
Content preview from 達人に学ぶDB設計徹底指南書 第2版
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3-2
それではテーブルについて詳しく見ていこうと思います。まずいくつか用語を整
理しておきましょう。
通常の表と同様に、テーブルにおいても横と縦のデータの組を「行」と「列」と
呼びます（図 3-1）。あるいは「レコード」と「カラム」という呼び方もします。こ
れは特に違和感のない呼び名だと思います。第 2 章でエンティティについて解説し
たときに、列を「属性」という呼び方もする、と言いましたが、実務ではほとんど
使わない表現なので、本書でも基本的に「列」という呼び名を採用します。
表になくて（も良くて）、リレーショナルデータベースのテーブルになくてはな
らないものがいくつかあります。そのうちの一つが「（key）」です。何の「鍵」
かというと、ある特定のデータを引き出すための鍵です。特にリレーショナルデー
3
94
9
8
7
6
5
4
3
2
1
タベースでは、「あるレコード（1行とは限らない）を特定するための列の組み合わ
せ」という意味で使います。キーの種類にも複数ありますが、特に重要なものは、
以下の二つです。
「
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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.