SQL道 - SQLビジュアライザー

SQLDOU is an educational app that visualizes SQL query execution plans with animations.

Following PacketDOU (Network) and CloudDOU (Cloud), this is the third installment in the "Path" series. This time, the theme is "SQL." When you enter SQL, an execution plan is automatically generated, and you can follow the flow of data from the table through filtering, sorting, and joining to the final result, step by step, with animation.

【What you can learn】

【Full Scan vs. Index】
Why is a full scan without an index slow? How much faster can searches become with a B-Tree index? You can run the same SQL using both scan methods and compare the speed difference in real time.

【B-Tree Index (O(log n))】
Supports range searches and equality searches. You can see the mechanism for efficiently identifying the target row using a tree structure through animation.

【Hash Index (O(1)) [Pro version]】
A high-speed index specialized for equality searches. You can experience the difference between using Hash Index and B-Tree Index in actual execution time.

【WHERE / DISTINCT】
See real-time PASS/SKIP indicators to see whether each row passes the WHERE condition or is skipped. Duplicate removal in DISTINCT can also be observed step-by-step.

【JOIN [Pro version]】
Visualize how rows from two tables are combined. Understand the batch processing mechanism where the join is executed only after data from both sides is available.

【GROUP BY / ORDER BY [Pro version]】
Animate the internal processing of aggregation (COUNT, SUM, AVG, MAX, MIN) and sorting (ASC, DESC). Observe how batch processing occurs after all rows have arrived.

【Free-form Question Mode [Pro version]】
A new mode where you can define your own table names, columns, and row data, write, save, and execute your own SQL. Go beyond the scope of the learning materials and learn by recreating scenarios you might encounter in real-world work.

【Mission System (20 questions total)】

Learn step-by-step with 20 missions divided into 6 levels.

* Level 1: SELECT / WHERE (5 questions): Experience the basics of SQL
* Level 2: Scan Methods (4 questions): Understand the speed difference between full scan and indexes
* Level 3: ORDER BY / DISTINCT (3 questions): Sorting and duplicate removal [Pro version]
* Level 4: GROUP BY (3 questions): Visualize the operation of aggregate functions [Pro version]
* Level 5: JOIN (2 questions): How table joins work [Pro version]
* Level 6: Comprehensive Exercise (3 questions): Index optimization challenge [Pro version]

Each mission includes a prediction quiz. Learn not just by watching, but by thinking through the "predict → execute → check answer" cycle. Visualize your progress with star ratings (maximum 3).

[Educational Feedback]

* Automatic Comparison: Executes the same SQL with a full scan and index, automatically displaying the speed difference.
* Live Scan: Displays the checking of each row in real time (with PASS/SKIP judgment).
* Diagnostic Comments: Explanations based on the results (Pro version has 3 sections: "Why is it slow?", "How to improve?", and "Background Knowledge").
* Table Data Preview: Allows prediction while viewing actual data.

[Free Version / Pro Version]

Free Version:
* Level 1-2 Missions (9 questions)
* Basic Diagnosis (1-line comment)
* B-Tree Index
* Free Mode

Pro Version (One-time purchase):
* Unlocks all 20 missions (Levels 3-6)
* Detailed Diagnosis (3 sections: Why/Improvement/Background Knowledge)
* Hash Index Support
* Advanced SQL (JOIN / GROUP BY / ORDER BY / (DISTINCT)
- Free-form question mode (Save and execute your own table and SQL)
- Ad-free

【Recommended for:】
- Students and new engineers learning the basics of SQL
- Those who want to intuitively understand "why indexes are fast"
- Database beginners who want to learn how to read execution plans
- Those looking for supplementary materials for classes or training
- Those who want to solidify the basics of SQL performance tuning