DATARAKU vs SQL Quiz Drills

An educational visualization app that lets you UNDERSTAND data structures by watching them - not by reading. Abstract concepts like stacks, queues, trees, and hash tables come alive as animations where the structure itself deforms in response to your operations. [ Basics - 4 structures ] - Stack (LIFO) - Feel "last in, first out" through stacking motion - Queue (FIFO) - Watch the entry and exit ends of a queue - Array - Visualize random access and the shifting of elements on insert / delete - Linked List - Nodes connected by arrows, rewired on insert and delete [ Advanced - 4 structures ] - Binary Search Tree - Values drop into place after branching left or right by comparison - Heap - Up-heap and down-heap motion in a complete binary tree - Hash Table - Keys travel through a hash function and land in a bucket - Graph - Nodes and edges showing adjacency [ Features ] - Every operation animates as a continuous deformation (no instant teleporting) - Operation log to review the meaning of each step - Each structure includes complexity notes (access / search / insert / delete), pros and cons, and real-world usage examples - Ads are never shown while an animation is playing - designed to preserve focus - Universal app for iPhone and iPad - Japanese and English (follows OS language) [ Who is this for ] - Students learning programming for the first time - Anyone preparing for IT exams - Engineers who want to re-grasp data structures visually - Curious minds who love watching things move [ Companion to ARURAKU ] The second information-systems title of the Raku Series, sibling to ARURAKU (algorithm visualization). The two apps cross-link, so the heap screen here links to ARURAKU's heap sort, and the graph screen here links to ARURAKU's BFS / DFS. Learn the "motion of computation" and the "structures that carry it" side by side. [ Note on pricing ] This app is completely free with no in-app purchases or subscriptions. To support development and maintenance we display Google AdMob banner and interstitial advertising. Ads are never shown while an animation is playing.

■ No engine required. Run SELECT in your head. SQLのエ is an iPhone app for practicing SQL in spare moments. Browser-based SQL playgrounds require sitting down at a PC; this app trades the engine for high-density questions, building real SQL skill through quick quizzes, repetition, and clear progress. ■ Who it's for - New engineers who want SQL at their fingertips - Analysts who need to read the SQL behind BI tools - Anyone preparing for database/IT certification exams - People who write SQL "by feel" and want to truly understand it ■ SQL-focused question formats - Four-choice (fundamentals): quickly check syntax and terms - Result-table prediction: guess the output from a table + query (our signature format) - Fill-in-the-blank: memorize keywords - True/False: check knowledge with rhythm ■ Learning modes - Chapter training: basics through SELECT, WHERE, sorting, aggregates, GROUP BY, JOIN, subqueries, set operations - Test: no explanations, just a score - Oni (hard) training: 10 seconds per question, combos for streaks - Daily 5: a fresh hand-picked set each day ■ Built to keep you going - Streak (consecutive study days) - Total queries solved and overall accuracy - Per-chapter accuracy heatmap - Achievement badges ■ Readable by design - Dark theme with SQL syntax highlighting and monospaced font - Clear result-table display ■ Privacy-first - No account, no ads - Works fully offline - Learning data stays on your device (never sent out) "10 questions a day. Run SELECT in your head." Make SQL a habit, starting today. Note: The app does not execute real SQL. To try queries for real, use the external links (e.g., DB Fiddle) in Settings.