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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60
レコードを取得する
3-7
ユーザー情報を保存しているテーブルから連絡先を確認したいときや、
スケジュールを保存しているテーブルから今日の予定を確認したいとき
は、テーブルに保存されているデータを取得する必要があります。そのよ
うな場合に、
ことができます。
テーブルに保存されているレコードを取得するときは、「SELECT」
文を使い、取得対象のテーブルの名前を指定します。
図3-16 は「menus」テーブルからデータを取得する例です。コマンド
を実行すると、テーブルに保存されているすべてのデータを取得すること
ができます。
図3-16 のように「SELECT」の後ろに「*」を指定した場合は、テーブ
ルからすべてのカラムの値が確認できます。一方「*」の代わりにカラム
名を指定すると、指定したカラムの値だけを見ることができます。
例えば図3-17 のように「SELECT」の後ろに「name」と指定すると、
「name」カラムの値のみを取得することができます。
カラム名は「,」で区切って複数指定することができます。
図3-17 のように、「name」のところを「name,category」のように置き
換えると、「name」と「category」カラムの値を取得することができま
す。このようにして、
...
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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.