SQL LeetCode Solution: Identifying Top Student Learning Paths

✅ Solved a SQL problem on LeetCode — Day 47 of my SQL Journey 💪 Learning doesn’t always move in a straight line… sometimes it spirals 🔄 Today’s problem was about identifying students who follow a study spiral pattern — studying multiple subjects in a structured, repeating cycle. The approach: • Tracked session order using ROW_NUMBER() • Measured gaps between sessions with LAG() and DATEDIFF() • Filtered sequences with gaps longer than 2 days • Detected repeating cycles using MOD() on row position • Counted students with at least 3 subjects across multiple cycles What I practised: • Window functions for sequence tracking • Time gap detection using date functions • Sequential pattern recognition • Using HAVING for conditional aggregation What stood out — A single session tells you nothing… A sequence tells you everything. Patterns don’t announce themselves, They hide in the order of events. That’s where the real insight lies. SQL doesn’t just query data. It helps read the story behind it. Consistent learning, one query at a time 🚀 #SQL #LeetCode #DataAnalytics #LearningInPublic #SQLPractice

💡 One SQL Lesson That Changed My Approach Recently, I realized that writing a query is easy… but writing an efficient query is the real skill. While working on a large dataset, I noticed performance issues. After optimizing indexes and rewriting joins, the query execution time dropped significantly 🚀 👉 Key takeaway: Always think beyond “working code” — focus on performance and scalability. #SQL #DataEngineering #Learning #CareerGrowth

Back with Day 2 of my 30 Days SQL Series 🚀 I wasn’t able to stay consistent for a few days, but I’ve decided to restart and stick to it this time 💪 💡 Today’s Learning: Solved 2 beginner-friendly problems, but they really helped me strengthen my fundamentals. 🔹 Problem 3: Big Countries The task was to filter countries based on large area or high population. This helped me understand how the OR condition works in SQL — even if one condition is true, the row gets selected. Note: Also realized that using AND here would have given a completely different result. AND : The AND condition returns results only when all conditions are true. 🔹 Problem 4: Article Views In this problem, I had to find authors who viewed their own articles. This was done using the condition author_id = viewer_id, which checks if both values are exactly the same. ⚡ Important Learning (Concepts I Used): WHERE → used to filter rows based on a condition = (Equality Operator) → checks for exact match between two columns DISTINCT → removes duplicate values and returns only unique results AS → used to rename a column (aliasing) for better readability ORDER BY → used to sort the result By default, it sorts in ascending order (small to large) These small concepts make a big difference when writing correct SQL queries. Focusing more on understanding the logic behind queries rather than just solving them. On to Day 3 💪 #SQL #LearningInPublic #Day2 #Consistency #DataAnalytics

Lately, I've been diving deeper into SQL, practicing intermediate concepts like CTEs and window functions, and it's been both exciting and humbling at the same time. 🚀 What I've realized during this phase is something simple but powerful. No matter how advanced the topic gets, everything still stands on the strength of the basics. We can learn how to write complex queries using CTEs, use logic with window functions, and solve problems, but if the understanding of fundamentals like JOINS, aggregations, filtering, etc. isn't solid, things start to fall apart pretty quickly. Practicing daily has taught me that growth isn't just about moving forward to harder topics, but also about constantly revisiting and strengthening the foundation. 🧠 Right now, I'm focusing on: • Practicing intermediate SQL concepts • Using core fundamentals alongside them • Building the habit of thinking through problems It's a slow process, but a meaningful one. If you're learning too, don't rush past the basics, they're doing more work than you think. ✨ #SQL #DataAnalytics #Consistency #Growth #Learning

Day 7 at Tap Academy – SQL Learning Journey 🚀 Today’s session focused on SQL operators and logical conditions. Here’s what I learned: 🔹 Continued learning SQL Operators 🔹 Explored Logical Operators: AND, OR, NOT 🔹 Learned and practiced: • DISTINCT – to retrieve unique values • BETWEEN & NOT BETWEEN – for range-based filtering • IN & NOT IN – for matching multiple values • IS NULL & IS NOT NULL – to handle missing data • LIKE – for pattern matching 🔹 Practiced writing queries using logical conditions 🔹 Solved problems to improve query-building skills 🔹 Got introduced to Escape Characters in SQL Building strong fundamentals step by step with consistent practice! #SQL #LearningJourney #TapAcademy #Database #100DaysOfCode #StudentLife

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✅ Solved a SQL problem on LeetCode — Day 43 of my SQL Journey 💪 Text looks simple… until you try to handle every edge case ✍️ Today’s problem was about transforming text — capitalising the first letter of each word, while handling special cases like hyphens correctly. I used recursive logic and string operations to: • Break text into individual characters using recursive CTE • Track previous characters using window functions • Identify word boundaries and special cases • Apply conditional uppercase/lowercase transformations • Reconstruct the final string using GROUP_CONCAT What I practised: • Recursive CTEs for step-by-step processing • Using LAG() to track character-level context • Writing precise CASE conditions for formatting • Handling edge cases like hyphenated words What stood out — Text transformations aren’t just formatting… they’re about handling context. A single character can change the logic, and missing one condition can break everything. That’s where attention to detail matters most. SQL isn’t just for numbers and aggregations. It can handle complex text logic too. Consistent learning, one query at a time 🚀 #SQL #LeetCode #SQLPractice #DataAnalytics #LearningInPublic

🚀 Day 48/100 – SQL Practice (LeetCode) ✅ Problem Solved: Count Unique Subjects per Teacher Today I worked on a SQL problem where I had to find how many unique subjects each teacher teaches. 💡Query: SELECT teacher_id, COUNT(DISTINCT subject_id) AS cnt FROM Teacher GROUP BY teacher_id; 🔍 My Approach: Used COUNT(DISTINCT subject_id) to avoid duplicate subject entries Applied GROUP BY teacher_id to calculate results for each teacher separately 📌 Problem Summary: Given a table with teacher_id and subject_id, the goal is to count how many different subjects each teacher is handling. 🚀 What I Learned Today: Difference between COUNT() and COUNT(DISTINCT ...) Importance of grouping in SQL queries Writing clean and correct aggregate queries ✨ Small step today, but building strong SQL fundamentals for the future! #Day48 #100DaysOfCode #SQL #LeetCode #Database #CodingJourney #DataAnalytics #LearnSQL #TechSkills #Consistency #GrowthMindset

🚀 Day 7 of My SQL Learning Journey Today I learned about CASE WHEN in SQL, a powerful feature used to apply conditional logic inside SQL queries. It works similar to IF–ELSE logic in programming and helps transform raw data into meaningful insights. 📚 Topics Covered: 🔹 CASE WHEN (Conditional Logic) Learned how CASE WHEN is used to show different results based on conditions within a query. 🔹 SUM + CASE WHEN Practiced combining SUM with CASE WHEN to calculate totals for specific conditions, such as total sales for a particular product category. 🔹 COUNT + CASE WHEN Used COUNT with CASE WHEN to count rows that satisfy certain conditions, such as counting pass/fail students or active customers. 🔹 CASE WHEN Syntax Rules Understood that every CASE statement starts with CASE and ends with END, with conditions defined using WHEN and results returned using THEN. 🔹 CASE WHEN with GROUP BY Learned how CASE WHEN can be applied with GROUP BY to perform conditional calculations on grouped data. 🔹 CASE WHEN with WHERE Explored how CASE WHEN can help apply dynamic filtering conditions inside the WHERE clause. 💡 Key Learning: CASE WHEN allows us to add decision-making logic directly inside SQL queries, making it easier to create conditional calculations and customized reports. #SQL #SQLLearning #DataAnalytics #LearningJourney #Database #DataSkills

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