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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9-4
本章では、木構造をリレーショナルデータベースのテーブルでどのように扱う
か、その方法論を二つ見てきました。各モデルをまとめると、以下のようになりま
す。
最も古典的なモデル。かつては検索／更新ともに複雑な処理を必要としまし
たが、SQLの進歩により、再帰共通表式を使った柔軟な検索が可能になりま
した。更新処理も対象のノードに局所化されており、外部キーによる参照整
合性制約も付与することができるため、もしお使いのDBMSが再帰共通表式
をサポートしていれば、木構造を扱うのモデルとなります
（Oracle、SQL Server、Db2、PostgreSQL、MySQLといった主要なDBMS
の最新版であれば再帰共通表式はサポートされています）。まだ大規模な木で
の再帰計算のパフォーマンス( 速度だけでなくリソース消費の観点でも) が未
知数なのが懸念点です。
すべてのノードについての経路を持つモデル。検索は柔軟で更新もそれほ
ど複雑ではないため、隣接リストモデルが採用できない古いバージョンの
DBMS を利用している場合のセカンドチョイスとなります。常に二つのテーブ
ルの同期を取る必要があることと、更新が難しいとは言わないまでもいささか
面倒である点に留意してください。
リレーショナルデータベースの論理設計といえば正規化と非正規化のトレードオ
フのせめぎあい、という印象が一般的です。しかしトレードオフのせめぎあいは他 ...
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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.