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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本節は、3-4節の「第1正規形」と7-2節の「非スカラ値（第1正規形未満）」の
続きです。「やれやれ、またスカラ値と配列型の話か」と思うかもしれませんが、
またその話です。このポイントは、それだけ難しく、誰もが設計に悩む箇所なので
す。それだけに、本節で重点的に解説しておきます。
7-2節では、非スカラ値を認める配列型を紹介しました。驚いた方もいるかもし
れませんが、リレーショナルデータベースは、この配列型を原則許可してしまった
のです。現時点において配列型の使用は、アンチパターンに位置づけて良いのです
が、一方で配列型を使わずに配列を模倣する論理設計があります。それが本節で
紹介する「列持ちテーブル」です。別名「繰り返し項目テーブル」とも呼ばれます。
この列持ちテーブルは、3-4節の「第1正規形を作ろう」でも一度紹介したこと
があります。再び「扶養者」テーブルをサンプルに使うと、以下のような構造のテー
ブルでした。
000A 加藤 達夫 信二
000B 藤本
001F 三島 敦 陽子 清美
JavaやCといったプログラミング言語であれば、kodomo[0]、kodomo[1]、
kodomo[2]……のような形で子のデータを配列に保持します。それをテーブルの
「列」を使って模したのが、この列持ちテーブルです。この構造のテーブルは、わ ...
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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.