一問から身につく SQL vs HelloSQL

【一問から身につく SQL とは】 SQLを「一問ずつ」確実に身につけるための学習アプリです。ストーリーとテーブル・データを見ながら、選択式の問題に取り組めます。解説では「なぜそうなるか」「よくある誤解」「実務ワンポイント」まで丁寧に解説し、暗記だけで終わらない理解を目指します。 【主な機能】 ・選択式の問題形式（ストーリー／テーブル・データ／SQL の見やすい構成） ・正解・不正解の履歴に基づく進捗表示 ・「誤答のみ表示」で苦手だけを集中的に復習 ・解説でつまずきやすい点を補強 【収録問題について】 リリース時点では全11問を収録しています。今後も問題を追加し、アプリアップデートで順次お届けする予定です（追加のタイミングや本数は開発状況により変わります）。 【料金】 ・一部の問題は無料で学習できます ・無料範囲を超える問題は、アプリ内課金（買い切り）でまとめて解放できます ・購入の復元に対応しています 【データ・プライバシー】 学習の進捗や解答履歴は、お使いの端末内に保存されます（当アプリ専用のアカウント登録は不要です）。 【利用規約】 本アプリの利用規約は、次のページでご確認いただけます。 https://root75125.github.io/sqlProblemPrivacy/terms-of-service.html ※本アプリの学習内容は一般的なSQLの理解を助けるものであり、特定の試験や資格の合格を保証するものではありません。

SQL tends to make sense while you're reading about it, then fall apart the moment you try to write it yourself. HelloSQL is for the writing part. You read a problem, write a query, and run it. The results show up as a table, and if they're right, it's marked correct right away. Grading looks at what your query returns, not how it's written, so your query doesn't have to match ours. There are 120 exercises, and most of them look like everyday reporting tasks. For example: "List payments from largest to smallest. If two amounts are the same, put the older one first." The practice data is built around an online store's orders, employee attendance, and billing for a subscription service. What's free and what isn't The first 30 exercises are free, and you don't need an account. They cover SELECT, WHERE, ORDER BY, and LIMIT. The other 90 move on to aggregate functions, GROUP BY, HAVING, INNER JOIN, LEFT JOIN, CASE, subqueries, CTEs, and window functions. You unlock all of them with one in-app purchase. There's no subscription and nothing recurring. When you're stuck Each exercise has three hints, and you open them one at a time. The first gives you only the idea. If that's not enough, the second shows the shape of the query, and the third tells you which tables and columns to use. We set it up this way so you don't have to jump straight to the answer. There's also a sample solution with an explanation, and you can tap any underlined term in a problem to see what it means. Coming back to it Your drafts save automatically, so you can close the app halfway through a query and finish it later. Missed exercises and bookmarks are kept together so you can try them again. Anything you get wrong comes back the next day. Exercises you get right come back too, after 3 days, then a week, then 3 weeks. The editor suggests SQL keywords and column names as you type, and you can look at the tables and their data at any point. It works on iPhone and iPad, in light or dark mode. If you've gone through a course or a book and want to actually use what you learned, this is a good next step. It also works as a warm-up before a SQL test or a technical interview. Before you download • The practice data is set in Japan, so some names, places, and text values are in Japanese. A few exercises ask you to type Japanese text into your query, such as WHERE city = '東京'. The exercise shows you the exact text to use. • You can practice and check answers offline. You only need a connection to buy or restore the unlock. • There are no ads. Exercise 1 is a single line that pulls every customer's name. It's a good place to start.