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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C0001 A 商事 000A 加藤 40 D01 開発
C0001 A 商事 000B 藤本 32 D02 人事
C0001 A 商事 001F 三島 50 D03 営業
C0002 B 化学 000A 斉藤 47 D03 営業
C0002 B 化学 009F 田島 25 D01 開発
C0002 B 化学 010A 渋谷 33 D04 総務
このテーブルを使えば、たとえば、直前に上司から受けた依頼「田島さんの会社
と所属の部署名」を得るに当たって、結合を使わずに済みます。
SELECT
会社
,
社
,
FROM
社
WHERE
社
= '
';
正規化したテーブル群におけるSQLと比較すると、非常にすっきりシンプル
で、簡単なSQL になることがわかります。しかも見た目が単純である以上に重要
なポイントは、結合を利用しないためパフォーマンスが良い、というところです。
42
一方、正規化（非正規化）と更新処理の関係はどのようなものになるのでしょ
うか？ 実は、このケースにおいては、正規化のほうに軍配が上がります。たとえ
ば、A商事が企業買収の対象になって、E物産という会社に吸収された場合を考え
ます。このとき、第2 正規化以前の「社員」
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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.