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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7-4
次に紹介するのは、ダブルミーニングの応用版です。現実には、単純なダブル
ミーニングよりもこちらのほうが、見かける頻度が高いパターンです。
第 3章において、社員情報を管理するテーブルをサンプルとして、第3正規化ま
で行ないました。その結果、最初は一つのテーブルにすべての情報を保持していた
のですが、最終的に「会社」「社員」「部署」という三つのテーブルに分離すること
になりました。
この三つのテーブルを眺めていると、あることに気づきます。それは、「会社」
テーブルと「部署」テーブルが、構造的に同じ形をしている、ということです。こ
の両テーブルは、ともに「識別 ID」＋「名称」という形をしています。
C0001 000A 加藤 40 D01
C0001 000B 藤本 32 D02
C0001 001F 三島 50 D03
C0002 000A 斉藤 47 D03
C0002 009F 田島 25 D01
C0002 010A 渋谷 33 D04
C0001 A 商事
C0002 B 化学
C0003 C 建設
D01 開発
D02 人事
D03 営業
D04 総務
236
7
9
8
7
6
5
4
3
2
1
ということは、この二つのテーブルは、あえて別々のテーブルにしてお ...
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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.