January 2021
Intermediate
240 pages
5h 32m
Japanese
Content preview from 図解まるわかり データベースのしくみ
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44
NoSQLデータベースの種類②
～階層構造と関係性を表すモデル～
2-7
ドキュメント指向型は、JSONやXMLと呼ばれる階層構造を持った形式
のデータを格納することができるモデルです（図2-15）。代表的なデータ
ベース管理システムに、MongoDBがあります。あらかじめテーブルの構
造を決めておく必要がなく、自由な構造のデータをそのまま取り込むこと
ができるという強みがあります。
例えばWebアプリケーションで普及している JSONデータには、複数の
項目が含まれており、項目ごとに配列やハッシュといった形でさらに深い
階層構造になっていることがよくあります。そのような複雑な構造をリレ
ーショナル型で格納する場合は、保存するデータを取捨選択し、各データ
の形を解析して適切な形に直して保存する必要があります。また、途中で
データ構造が変わった場合は、テーブル設計を新たに見直す必要も出てく
るでしょう。ドキュメント指向型では、受け取ったデータをそのままの状
態で格納することができるため、
。
グラフ型は関係性を表現するのに最適なモデルです（図2-16）。
例えばユーザーAがBと友達で、BはC、Dと友達、といったようなネ
ットワーク構造のデータを格納するのに長けています。今回の例だとユー
ザーA がノードと呼ばれ、各ユーザー同士のつながりをリレーションシッ
プ、そしてノードやリレーションシップが持つ属性をプロパティとして ...
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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.