SQLDOU vs Azure DP

SQLDOU is an educational app that visualizes SQL query execution plans with step by step animation. The third entry in the DOU series, following PAKEDOU (networking) and KURAUDOU (cloud). This time the theme is SQL. Enter a query and watch the execution plan generate automatically, then follow each row as it flows through filtering, sorting, joining and finally arrives at the result. WHAT YOU WILL LEARN • Full Scan vs Index Why scanning every row (full scan) is slow. See how much faster a B Tree index makes searches. Run the same SQL with both scan methods and compare speed in real time. • B Tree Index O(log n) Supports range queries such as greater than, less than, greater than or equal, less than or equal and equality. Watch the tree structure locate target rows efficiently through animation. • Hash Index O(1) Pro A high speed index specialized for equality searches. Experience the real execution time difference between Hash and B Tree. • WHERE and DISTINCT See each row pass or get skipped by the WHERE condition in real time with PASS or SKIP badges. Observe DISTINCT removing duplicates step by step. • JOIN Pro Visualize how rows from two tables are combined. See the batch process that waits for both sides before executing the join. • GROUP BY and ORDER BY Pro Watch aggregation such as COUNT, SUM, AVG, MAX and MIN and sorting such as ASC and DESC animate their internal processing. Observe how they buffer all rows before producing output. • Custom Quiz Mode v3.0 Pro Define your own table name, columns and rows, write any SQL you want, and save the quiz. Replay or edit later. Go beyond textbook examples and reproduce real world scenarios you care about. 20 MISSIONS Progress through 20 missions across 6 levels. • Level 1 SELECT and WHERE 5 missions SQL fundamentals • Level 2 Scan Methods 4 missions Full scan vs index speed comparison • Level 3 ORDER BY and DISTINCT 3 missions Pro • Level 4 GROUP BY 3 missions Pro • Level 5 JOIN 2 missions Pro • Level 6 Final Challenge 3 missions Index optimization Pro Each mission includes a prediction quiz. The Predict Execute Verify cycle encourages active learning. Star ratings up to three track your progress. EDUCATIONAL FEEDBACK • Auto comparison run the same SQL with full scan and index and see the speed difference automatically • Scan narration watch each row being checked in real time with PASS or SKIP verdict • Diagnostic comments context aware explanations Pro Why slow How to improve Background knowledge • Table data preview see actual data while making predictions FREE AND PRO Free • Level 1 and Level 2 missions total 9 missions • Basic diagnostics one line comment • B Tree index • Free mode Pro one time purchase • All 20 missions unlocked • Detailed diagnostics Why How to improve Background • Hash index support • Advanced SQL JOIN GROUP BY ORDER BY DISTINCT • Custom Quiz Mode build save and run your own quizzes • No ads WHO IS THIS FOR • Students and junior engineers learning SQL basics • Anyone who wants to intuitively understand why indexes are fast • Database beginners learning execution plans • Instructors looking for training supplements • Developers building a foundation in SQL performance tuning

Prepare for Azure DP-300 SQL Solutions with one connected flow from core concepts to practice, review, and mock exams. Official credential reference: Microsoft Azure Database Administrator Associate (DP-300) The current question bank contains 532 questions. Study in 50-question sets or focus by domain, subdomain, and difficulty. Single-select and multiple-select items are supported where applicable. Immediately after answering, check the correct-answer explanation and the reasoning for every choice so you understand both why the answer is correct and why the alternatives do not fit. Structured study and records • 50-question set learning plus domain, subdomain, and difficulty filters • Immediate grading, correct-answer explanations, and choice-by-choice rationales • Separate saved progress and resume for set, domain, and difficulty study and for mock exams • A study-history calendar with daily question and key-term activity, monthly totals, and study streaks • Review of wrong answers, repeated misses, review notes, and weak-area analysis • Timed mock exams that hide explanations until submission, allow answer changes before submission, and show results by domain • Weekly goal reminders with a configurable notification time • Light, dark, and system themes A smooth learning flow Move quickly among Home, Study, Review, Mock Exam, and Settings. Each mode keeps its own learning state, and moving to the next item after a long explanation automatically returns the new question card to the top. Basic terms and optional audio study Use the basic-term flashcards as the primary memorization tool. When useful, turn on automatic audio playback to repeat key terms while walking, resting, or preparing for sleep without continuously reading the screen. The questions in this app are current as of August 2026, and we plan to review and update every exam’s question bank at least once a year. The questions are independently authored for study and do not reproduce live exam items, dumps, leaked questions, or third-party question banks. This is an independent study app and is not affiliated with, endorsed by, or sponsored by any certification body, exam provider, or trademark owner. Exam names and trademarks belong to their respective owners.