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
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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.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.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.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.
O
n
O
n
この領域における処理時間の差はごくわずかであるため、実際のところB-tree で
もフルスキャンでも大差はありません。しかし、それであればわざわざ無駄なイン
デックスを作る必要はありません。
では、その「データ量が少ない場合」というのがどの程度の閾
しきいち
値なのか、という
ところが気になるところです。これは、ストレージやサーバーの性能など環境要因
によって変わるために、固定的な値は存在しないのですが、最近のハードウェアを
考えるなら、目安としてはレコード数が10万件以下の場合はほぼ効果がないと考
えてもらってかまいません。
48
ただ、これはあくまで目安です。実際の閾値はシステムによって異なるため、あ
らかじめ簡単な実測を行なって感覚をつかむことをお勧めします。
B-treeインデックスを作成する列として適不適を判断するための最も重要な情報
が、です。これは、特定の列の値が、どのぐらいの種類の多さを
持つか、ということを表わす概念です。
たとえば簡単な例で、「性別」を表わす列を考えましょう。この列が持つ値とし
ては、次のようなものが考えられます。
200
6
9
8
7
6
5
4
3
2
1
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
Read now
Unlock full access
More than 5,000 organizations count on O’Reilly
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.