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
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.
122
ひとまとまりの処理を実行する
4-15
一連のトランザクションに含まれる処理が成功したときに、その結果を
データベースに反映させることをコミットと呼びます。
トランザクションを用いた場合、
（図4-29）。
銀行口座の例で考えてみましょう。A口座から B口座に 10 万円を送金す
るときは、データベース上ではトランザクションを用いて「A口座の預金
をマイナス10 万円にする」「 B 口座の預金をプラス 10 万円にする」といっ
た2 つの処理を実行し、最後にコミットを行います（図4-30）。
このとき途中経過は外から見えないので、他の処理からコマンド実行中
の値は見えず、A口座の値の更新直後に他の処理が入り込むことはありま
せん。B口座の値の更新も行い、最後にコミットを実行して初めてデータ
ベースに結果が反映され、他の処理からその値を読み取ることができるよ
うになります。
トランザクションの実行方法はデータベース管理システムによって違い
がありますが、MySQLの場合は、「STARTTRANSACTION;」を実行し、そ
の後にトランザクションを用いて実行したい処理を書いていきます。この
時点ではまだデータベースに結果は反映されません。最後に「COMMIT;」
というコマンドを実行することでコミットを行うことができ、データベー
スに変更内容が適用された状態となります。 ...
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.