Gabriel Mazzucco’s Post

Stop writing SQL "Inception." Use CTEs instead. 🛑📖 We’ve all been there: opening a query only to find a subquery, inside a subquery, inside another subquery. It’s hard to read, impossible to debug, and a nightmare for your future self. If you want to move from a "Junior" to a "Senior" SQL mindset, you need to master CTEs (Common Table Expressions). Why CTEs are a game-changer: Readability: They allow you to read code from top to bottom, like a story, rather than from the inside out. Reusability: You can reference the same CTE multiple times in one query. No more copy-pasting the same subquery logic! Debugging: You can test each "layer" of your data transformation individually before joining them all together. The Golden Rule: If your logic has more than two levels of nesting, it’s time for a WITH clause. #SQL #DataEngineering #Database #CodingTips #CleanCode #DataAnalytics #CareerGrowth

I used to think I "knew" SQL. Then I started building my own project and realized that "knowing" the syntax isn't the same as "understanding" the logic. I’ve spent the last few hours with Mosh Hamedani’s course, un-learning my bad habits. 3 things I’m focusing on today: JOIN Logic: Understanding exactly which "circle" of the Venn diagram I need. Subqueries: When to use them (and when they’re a performance trap). Optimization: Thinking like the Database Engine. Consistency isn't about how much you learn in a day; it’s about showing up even when the logic gets tough. Are you Team #SQL or Team #NoSQL for your personal projects? #CodeWithMosh #Backend #DeveloperLife #Consistency #TechGrowth

💥Hello mates!! (New challenges) 📌Kicking off my SQL 50 journey on LeetCode to sharpen my SQL skills Day 01 starts today! SQL 50 LeetCode (01/50): Today's problem is #1757:"Recyclable and low Fat products"👨💻 This is an Easy-level problem that focuses on filtering data using SQL condition. I used the WHERE clause to solve this problem,and it successfully passed all the test case✅️ How my solution Works: ->I used the WHERE clause to filter the records based on the given condition. ->The AND Operator ensure that only products that are both low- fat and recyclable are selected. ->Since the problem doesn't require any joins or aggregations, the query stays simple,clean and easy to understand. -> This approach reflect real-world SQL queries practices used in Data Analytics and Data Engineering task. Database Used:MySQL See you all tomorrow with another exciting LeetCode problem! #LeetCode #SQL50 #SQLQuery #DataAnalytics #Database #Coding #SQLPractice #Coding

📊 Recently, I took some time to revisit core SQL concepts while practicing query-based problems on LeetCode. It was a great way to strengthen fundamentals like: • JOINs and subqueries • GROUP BY & aggregation • Window functions • Writing optimized queries for real-world scenarios Along with problem-solving, I also revised important database concepts such as ACID properties and Normalization, which are essential for designing reliable and scalable systems. To keep everything in one place, I’ve created a concise PDF that includes: ✔ Common SQL queries (interview-focused) ✔ Clear explanation of ACID properties ✔ Normalization concepts with examples Sharing it here in case it helps others who are preparing for SQL interviews or brushing up their basics. #SQL #LeetCode #Database #BackendDevelopment #InterviewPreparation #LearningJourney

Stop writing "Nesting Dolls" in your SQL. 🪆 We have all seen it: A SQL script with subqueries nested 5 levels deep. It’s hard to read, impossible to debug, and a nightmare to maintain. In 2026, CTEs (Common Table Expressions) aren't just a "nice to have"—they are the standard for professional data pipelines. Why CTEs win every time: 1️⃣ Readability: They allow you to read code from top to bottom, like a story. 2️⃣ Reusability: Define a logic once and reference it multiple times in the same query. 3️⃣ Debugging: You can comment out the final SELECT and test your CTEs one by one. Pro-Tip: If your query is longer than 50 lines, it probably needs a WITH clause. Your future self (and your teammates) will thank you. #SQLTips #CleanCode #DataEngineering #AnalyticsEngineering #dbt

Solving the SQL 50 challenge on LeetCode has been an exciting and confidence-boosting journey. Each problem pushed me to think deeper, optimize queries, and strengthen my understanding of SQL concepts. From basic queries to advanced topics like joins, aggregations, subqueries, and window functions — this journey was truly enriching 💡 📘 What’s in my notes/document? A structured study guide covering: All 50 problems with solutions Clear explanations for each query Key SQL concepts like SELECT, JOINs, Aggregations, Window Functions, and more Practical patterns and best practices for real-world scenarios Once you get a solid grip on fundamentals, problems labeled medium or even hard start feeling like easy. It’s all about consistency and practice. #SQL #LeetCode #DataEngineering #LearningJourney #sql50

I used to write SQL like this… 😅 One long query. Nested subqueries everywhere. And when it broke? I had NO idea where the problem was. Then I learned about CTE. Everything changed. 👇 Instead of writing everything at once, I started breaking queries into steps. WITH step1 AS (...), step2 AS (...) Suddenly: ✔ My queries became readable ✔ Debugging became easier ✔ Logic made more sense CTE isn’t just a SQL feature… It’s a way of thinking. If you're learning SQL, start using CTE today 🚀 #SQL #DataAnalytics #LearningSQL #CTE #CodeBasics

🤯 𝐒𝐭𝐫𝐮𝐠𝐠𝐥𝐢𝐧𝐠 𝐭𝐨 𝐜𝐡𝐨𝐨𝐬𝐞 𝐛𝐞𝐭𝐰𝐞𝐞𝐧 𝐂𝐓𝐄𝐬 𝐚𝐧𝐝 𝐒𝐮𝐛𝐪𝐮𝐞𝐫𝐢𝐞𝐬 𝐢𝐧 𝐒𝐐𝐋? Not every SQL problem is hard… sometimes it’s just about choosing the better way to write it. Here’s a simple breakdown 👇 🔹 𝐂𝐓𝐄𝐬 (𝐖𝐈𝐓𝐇 𝐜𝐥𝐚𝐮𝐬𝐞) • Defined before the main query • Makes complex queries more structured • Improves readability and debugging • Can be reused within the same query • Supports recursive logic 🔹 𝐒𝐮𝐛𝐪𝐮𝐞𝐫𝐢𝐞𝐬 • Written inside another query • Useful for quick filtering and conditions • Can become harder to read when nested • Limited reusability 📊 𝐖𝐡𝐚𝐭 𝐭𝐡𝐢𝐬 𝐦𝐞𝐚𝐧𝐬 𝐢𝐧 𝐩𝐫𝐚𝐜𝐭𝐢𝐜𝐞: • Both approaches can solve the same problem • The difference comes in clarity and maintainability • As queries grow, structure starts to matter more 💡 𝐒𝐢𝐦𝐩𝐥𝐞 𝐰𝐚𝐲 𝐭𝐨 𝐝𝐞𝐜𝐢𝐝𝐞: • Small & straightforward task → Subquery • Multi-step or complex logic → CTE 💬𝐖𝐡𝐚𝐭 𝐝𝐨 𝐲𝐨𝐮 𝐮𝐬𝐮𝐚𝐥𝐥𝐲 𝐩𝐫𝐞𝐟𝐞𝐫 𝐰𝐡𝐢𝐥𝐞 𝐰𝐫𝐢𝐭𝐢𝐧𝐠 𝐒𝐐𝐋? #SQL #DataAnalytics #DataAnalyst #PostgreSQL #LearningInPublic #SQLTips #CTE #Subquery

🚀 Day 36 of My SQL Learning Journey Today I worked on a challenging SQL problem involving consecutive records and learned an important lesson along the way 🔥 🔹 Problem: Find records where people count is ≥ 100 for at least 3 consecutive entries 🔗 Problem Link: https://lnkd.in/gNBER5CQ 🔹 Final Solution: WITH temp AS ( SELECT id, visit_date, people, id - ROW_NUMBER() OVER (ORDER BY id) AS grp FROM Stadium WHERE people >= 100 ) SELECT id, visit_date, people FROM temp WHERE grp IN ( SELECT grp FROM temp GROUP BY grp HAVING COUNT(*) >= 3 ); 🔹 Key Learning 💡: The approach was to use ID-based grouping, because the problem depends on consecutive entries (IDs), not consecutive dates. 🔹 Concepts Used: ROW_NUMBER() for sequence handling Grouping consecutive records Window functions + aggregation 💡 Debugging mistakes helped me understand the problem more deeply than just solving it! Consistency continues 🚀 #SQL #LeetCode #WindowFunctions #ProblemSolving #90DaysOfCode #CodingJourney

Understanding the difference between RANK, DENSE_RANK and ROW_NUMBER in SQL can make a big difference in both interviews and real-world data analysis. A simple and clear explanation of SQL Ranking Functions is now live on CodeQueryHub. This video covers: • How RANK() works and why ranks get skipped • Difference between RANK() and DENSE_RANK() • How ROW_NUMBER() assigns unique values • Category-wise ranking using PARTITION BY • Key concepts often asked in SQL interviews This is Part 2 of the Window Functions series. Watch here: https://lnkd.in/gn7AkRRG #SQL #RankingFunctions #WindowFunctions #LearnSQL #SQLTutorial #SQLForBeginners #DataAnalytics #DataScience #DataAnalyst #DataEngineer #SQLQueries #SQLPractice #SQLLearning #Analytics #Database #DatabaseManagement #MySQL #PostgreSQL #OracleSQL #SQLServer #Programming #Coding #TechLearning #CareerGrowth #CodeQueryHub